In the far future, T-Mat Control on Earth is a hive of activity. It is the central point on the planet for an instantaneous form of global travel; using travelmat cubicles people and things can be moved instantly from one place to another. A computer voice announces all shipments, almost all of them completed as soon as they begin. Almost all. A shipment of badly-needed synthetic protein from New York to Moscow has gone awry, which the computer mention several times.

Technical Coordinator Gia Kelly, a cool and controlled manager, asks her assistant Brent to explain the New York to Moscow trouble. He says the trouble is with the relay station on the moon. The Moscow shipment has been mistakenly routed to Canberra. Both of them suspect a perpetual troublemaking crewman on the moon, a man called Fewsham. By isolating the Canberra-Moscow link, they solve the problem.

A T-Mat cubical in the control area activates and a man materialises. He is pleasant and happy, that is until he speaks to Miss Kelly. His name is Osgood and he apparently had the bad fortune to recommend Fewsham for the Assistant Controller position on the moonbase. Whenever anything goes wrong, it falls to Osgood to set it right. Osgood still feels that he did the right thing in recommending Fewsham as he felt the lad deserved a break, but Kelly accuses him of needless sentiment. She tells Osgood testily that all T-Mat shipments are now 5 minutes behind schedule thanks to Fewsham's mistake. Osgood is back to pleasant again as he sets off by T-Mat for the moon, blowing the disgusted Kelly a kiss as he goes.

Luckily for them all, the situation is back to normal before the Controller arrives. They all breathe a sigh of relief about that. Shortly, he does arrive by T-Mat, Commander Julian Radnor, a stern civil servant who must always balance the political and the practical. He couldn't have chosen a better person as Technical Controller. Kelly's cool efficiency is just the complement for Radnor's more difficult glad-handing role. All seems well for now.

On the moonbase, Osgood is giving a contrite Fewsham a dressing-down for his mistake. Fewsham protests that he was on duty all night, but Osgood doesn't accept it. His own career is on the line because of Fewsham. For his part, Fewsham is very sorry, as he clearly owes his job to his friend. The slight, mousy man would never have made Assistant Controller on his own. Osgood relents because everything is now back on schedule and orders Fewsham back to Earth for a good long rest.

However, before he enters the cubicle, an alarm goes off. Someone is using the outer airlock without authorisation. Suddenly there is a scream. They open the doors and crewman Phipps staggers in, a look of shock and abject fear on his face. Another scream and two more crewman race in. In the corridor, the unseen invaders bear down on the control room. Osgood orders all his men to stay still, but one of them is too frightened to obey. He tries to run for an exit but is caught by the blast from some sort of ray gun. His body distorts and he crumples to the floor, dead. The invaders enter.

On Earth, another moonbase delay registers. Unfortunately, it is the second part of the Moscow consignment, a potential political hot potato. Kelly tries to reach Osgood via videolink but the screen stays blank. This is too much. There's going to be serious trouble for Osgood this time.

Back on the moonbase, Osgood's career is the last thing on his mind. He has been ordered by the invaders to disrupt the T-Mat link with Earth. Osgood refuses. The leader of the invaders, speaking in a low, sibilant, hissing voice, tells him he must do so or he will die. Osgood goes to the control panel but instead of turning over T-Mat to the invaders, he deliberately overloads the system so that it is useless. For his efforts, he is destroyed.

The entire T-Mat system is now out all over the world. Commander Radnor is furious at the lapse in his system and even angrier that there seems to be no explanation for it. All checks this end show no faults. And all communication with moonbase are out so nothing can be checked there. Radnor demands answers from his staff, and he wants them quickly.

Elsewhere, the TARDIS makes a nice smooth landing. However, the scanner shows a rocket against a starry backdrop and it looks like they're suspended in space once again. When the Doctor turns the scanner control, the monitor shows a man in an old-fashioned space suit very near. It looks as if he's trying to climb aboard. The Doctor notes at least a century's development between the two items. Soon it becomes clear to the Doctor and another twist of the knob proves him right, showing a piece of parchment with Leonardo DaVinci's flying machine. They've landed in a space museum and these are all displays! The astronaut is Yuri Gagarin, first man in space. There are also images of balloons, shuttles, everything. The Doctor is excited and wants to go outside and explore.

They look through all of the displays, very interested. Zoe finds an interactive display and turns it on. A screen lights up, explaining all about Travel-Mat, or T-Mat for short. Instantaneous travel to any place in the world. Jamie likens it to travel in the TARDIS, except T-Mat is reputed to be foolproof. Their investigations are curtailed, however, when they find a gun being pointed at them.

Assistant Controller Fewsham is now the ranking officer on moonbase and the invaders turn their attention to him. If he does not want to die like Osgood, he will repair the damage to T-Mat and get the system working again. Fewsham is nearly numb with fear but knows he doesn't have the technical expertise to execute the repairs. Neither do the other two, Locke and Phipps. They are maintenance only. They tell the leader of the invaders that only Gia Kelly has the knowledge to repair the damage, but she can't be brought here because T-Mat is down. The video link is also down. They are completely cut off.

The leader, a slim green bipedal figure in some sort of armour, thinks they are exaggerating. When he orders all of the humans destroyed, Fewsham gives in and tells him of the emergency T-Mat link to Earth. Unfortunately, it is damaged too. The leader will give them time to repair it. If not, they will all die. They are left alone with a guard on the door.

Fewsham is ready to start work at once, desperate to do anything to prolong his life. Phipps and Locke refuse to help, determined to stop these invaders from travelling to Earth, which must be their goal. Fewsham reminds them of Osgood's horrific death, frightened almost out of his mind by the image. He doesn't want to die like that and he'll do anything to survive. Anything. Including capitulating to the invaders.

On Earth, Brent and his people have completed their checks of T-Mat. There are no faults anywhere on Earth. The fault must be on the moon, but there is absolutely no way to investigate. There are no answers and no solutions. This news angers Radnor, who has senior government officials hounding him for answers. But there are none, unless they can get to the moonbase. Kelly tries to inject some levity by suggesting a rocket trip to the moon, which brings dry laughter from Brent. However, Radnor takes this seriously. To him, it is actually a solution - perhaps the only one.

Kelly and Brent are stunned. The only rockets that exist now are in museums. No one knows how to make one operational, let alone fly one. For once, Miss Kelly is wrong, and Radnor knows it. There is just one man who can do all of this - the man they need.

By the coincidence which seems to guide his life, the Doctor is meeting that man at this very moment. Unfortunately, he's the one holding the gun. He accuses them all of trespassing as his museum is closed to the public. He seems to buy their story that they came by T-Mat, even when he spots the police box sitting incongruously in the corner amidst the exhibits. His name is Eldred, Professor Daniel Eldred, and he wants them to leave here immediately.

Zoe and the Doctor protest that they are genuinely interested in the displays and in space travel but Eldred finds this hard to believe. The only reason anyone wants to visit here is to laugh at him and his "antiquated machines", or to steal his artefacts. The Doctor is stunned that any of this is looked down upon. His true enthusiasm for rocketry slowly wins over Eldred, who explains that T-Mat has made rockets obsolete almost overnight and ended man's desire to explore beyond the moon. He and the Doctor get lost in descriptions of an ion jet rocket model, Eldred's pride and joy.

Eldred designed the rocket and is the last such person in the world. T-Mat ended all space travel. Rockets aren't even kept around as an auxiliary means of travel - T-Mat was though infallible. He lost government backing for his rocket program, although he hasn't given up on once again seeing rockets in space.

Fewsham tries again to persuade his men to help him repair T-Mat. He fears he can't do it on his own but they clearly have no respect for his rank. In fact, they decide to take another course of action. Locke checks over the video link and determines that it's not as badly damaged as first thought. He and Phipps set to work on it in hopes of getting a message to Earth. Fewsham is beside himself with fear. They were told to fix T-Mat, not the video. If they're caught, they'll all be killed. Locke coldly tells his "superior" that he can do whatever he wants: this is their choice.

Professor Eldred appreciates the Doctor's genuine enthusiasm for space travel. He has had no one to share his bitter disappointment with for some time. He still wonders where the Doctor and his friends came from and thinks he has the answer when his door alarm sounds. Commander Radnor and Controller Kelly stand before him and Eldred assumes immediately that the Doctor and his friends are spies. Radnor denies this and the Doctor, Jamie, and Zoe move off to let them talk.

It quickly becomes clear that Eldred and Radnor are old friends, long estranged. In fact, Radnor worked with Eldred on rocketry at the very end, only to abandon it for T-Mat and its juicy government funding. Eldred is still bitter, even though he chose to ignore T-Mat and not join the project when he was invited. He preferred rockets then and still does now, as obsolete as they are.

However, Radnor knows that rockets are not just myths. He has known for a long time that Eldred has been secretly building an ion rocket for an unauthorised journey into space. Eldred is stunned to know his secret is common knowledge in the government and assumes that his "old friend" Radnor has come to shut him down. Amazingly, Radnor offers to help!

Radnor turns on the charm, telling Eldred that he can make his trip - with full government backing - as long as it is to the moon. Kelly explains about the "minor fault" in T-Mat and Eldred laughs heartily. The only way to fix T-Mat is by rocket. He finds the irony hard to ignore. Radnor hopes this means he will help, if only to prove he was right. But Radnor is mistaken as Eldred refuses to allow his rocket to be used.

Phipps and Locke have succeeded in reactivating the video link. Fewsham fears for their lives should the guard hear them using it. Locke goes ahead anyway.

The call is routed to Radnor via computer. He takes in on Eldred's communications unit. Locke appears but has time to say very little. Osgood is dead and they are in desperate trouble. Then the screen goes blank, cut off from the moon. Radnor can hardly believe what he's heard.

A green pincer-like claw destroys the video link and the leader of the invaders calls his guard forward. It is a green, lizard-like armoured warrior with a sonic gun built into its claw. It hisses when it breaths but is nonetheless tall, powerful, and frightening. Dubbed "Ice Warriors" when they were first discovered by humans during the second ice age, they are warriors from the planet Mars, warlike and ruthless. They have returned from their home. Their target: Earth.

Phipps runs from the control room, dodging fire from the warrior. The leader of the Ice Warriors, a slimmer, less-armoured version of them, orders his warrior to pursue the escapee. He then turns on the terrified Fewsham. Stammering, Fewsham says it is still possible to fix the emergency T-Mat link but he'll need time. The leader agrees, sparing him for now, but points to Locke's twisted body as a reminder of what will happen if he fails.

Commander Radnor faces an obstinate Professor Eldred, who still refuses to allow his rocket to be used to help the men on the moonbase and to restore T-Mat. The Doctor joins in, trying to make Eldred understand that this is a victory for him, and for rocketry. But Eldred still refuses. He admits that the hardware exists for a launch, but he fears that all the money and expertise in the world would not negate the dangers of such a flight. The equipment is unchecked, cobbled together on the sly. It just won't work. He knows that he is the only person experienced enough to fly the rocket and he is now too old to stand the trip. It cannot be done!

Jamie, Zoe, and the Doctor now hang back, listening. Jamie wants to help them somehow and suggests using the TARDIS, but even he is forced to admit that it would never land where it was intended. Still, he and Zoe wish to help somehow. The Doctor agrees and offers their services on the project. He says that he and his companions have great experience in space travel.

Radnor is pleased, thinking this will finally convince Eldred to agree. To his amazement, the old man still refuses. The risks are too great.

A call comes through to Radnor. Computer control reports widespread problems due to T-Mat breakdown. Vital food and medical shipments are stopped and outcry is being registered from all over the world. Professor Eldred takes this in and softens somewhat. Clearly the situation is serious and his rocket is all that can save the world from chaos. However, he still thinks the risk is too great, despite the Doctor's assurances. But Radnor is determined. He'll use that rocket with or without his old friend's help; he only hopes he can count on the vital assistance. Eldred knows they'll all need a miracle to succeed.

The warriors continue their search of the moonbase for Phipps. He is still free but there's little place for him to run. He hides out in the solar energy equipment stores, but is horrified when a warrior enters right behind him. To his utter amazement, the warrior fails to see him hiding in a corner. He is safe for the moment. But he did not come here by accident. He has a plan and begins unpacking some equipment.

Work on the rocket moves quite quickly, limitless personnel and money being available for this vital project. Kelly is satisfied with everything except the choice of crew. She knows very little about the Doctor and his friends and considers them quite odd. Radnor agrees but cannot deny Zoe and the Doctor's knowledge of space travel. Jamie, however, is a question mark and Radnor questions the Doctor about it. He had actually intended to leave the inexperienced lad behind, but Jamie bullies him into changing his mind. The rocket is intended for a crew of three and he's going to be one of them!

There is another problem, though, even more pressing - lack of fuel. There's barely enough for a two-way trip and no other source available on Earth. Eldred reminds them all of the fuel dump at the moonbase, abandoned intact after the last manned trip. Radnor mistrusts it due to lack of use, but Eldred reminds him that all the equipment is like that - intact but unused. If they trust one part of it, they must trust it all, especially the automatic homing beacon. If that's kaput, then a return trip won't even be necessary - they'll never make it to the moon in the first place!

As Eldred goes over flight procedures with the Doctor once again, Kelly talks to Radnor. She wants to go as one of the crew on the rocket. She is the only one who can repair T-Mat. Radnor rejects this, saying that she is too valuable to risk and is needed here. They must hope that at least one of the crewmen is still alive to assist the Doctor. Kelly thinks this a long shot, as is the success of the space journey. The Doctor assures her that he and his friends will be fine, it is only the situation on the moon that is in question.

Fewsham struggles with the emergency T-Mat link, motivated by fear. He has nearly succeeded despite constant harassment by the leader of the warriors. Fewsham plucks up the courage to ask what good this link will do - it is not adequate to transport an army. The leader, called Slaar, assures him that an army is not required. The Earth will be theirs for the taking, quite easily.

In the solar stores, Phipps struggles to create some sort of weapon against the invading warriors. He finds the equipment but must search high and low before he finds a solar power line hidden behind several pieces of disused junk.

Back on Earth, success has come to the team working on Professor Eldred's rocket. It is time for the lift off activation check. The Doctor, Zoe, and Jamie are ensconced in the crew capsule and everything looks to be functioning perfectly. No one can believe how quickly it all came together. The Doctor is anxious to get underway but Commander Radnor insists on going once again over post-landing procedure. The Doctor assures him he knows what to do - repair the video link with Earth so that Miss Kelly can advise him on repairing the T-Mat fault.

Three minutes of checks later, the countdown begins at a scant 60 seconds. Jamie brushes off the concerns of his friends, assuring him he's ready for these "G-forces" they've told him about, along with all the other dangers of space travel. There is, however, some trepidation in his voice despite the big words.

Trepidation reigns in launch control as well. Despite all the preflight checks, Eldred worries that the launch still won't go off. He's waited so long. But the countdown proceeds smoothly and soon the rocket hurtles toward the heavens. Radnor is awed, and so is Eldred. He never though he'd live to see such a sight again.

But duty calls and Eldred remembers he must establish contact with his astronauts. To his horror, the videolink is dead. Kelly tries the audio link and gets no response. They are afraid they've lost all contact with the rocket's crew!

The rocket races toward the moon. Jamie, Zoe, and the Doctor are feeling the effects of zero gravity. Luckily the rocket is equipped with an artificial gravity system. Zoe switches it on and they return to their seats. She then radios back to Earth, responding to the insistent and endless calls from launch control. Eldred reports the lost videolink, which the Doctor confirms as a fault on their end. Mercifully, he doesn't mention the smoke filling the cabin! Clearly the entire communications circuitry is faulty.

Hopefully, that's the only faulty system.

Meanwhile, on the moon, Fewsham succeeds in repairing the emergency T-Mat link with Earth. He is much calmer now. Slaar orders him to activate it - on "receive" only.

This news reaches Radnor and Kelly even as they worry over the fate of the rocket. All communication has now been lost. They don't even know if the rocket is still in one piece. Neither one of them can figure out why the emergency T-Mat link suddenly came back to life, nor why it is on "send" only, but it doesn't really matter. Kelly is prepared to go up there immediately and effect repairs. Radnor tries to prevent her, once again reminding her of her value to the T-Mat project and the dangers of travelling to the moon when they have no idea what conditions are like there. This time, however, the headstrong woman will not listen. She is the only one let who can repair the T-Mat system. She will do so with or without Radnor's permission. She heads for Earth control and the waiting T-Mat cubicle.

On the moonbase, Phipps has fashioned a set of solar power boosters which he hopes to use against the warrior, only they'll have to get very close indeed for him to even test it.

In the control room, Fewsham cools his heels alone. He watches as Miss Kelly and two technicians arrive via the emergency link. He is ready with a cover story to allay Kelly's suspicions. Osgood went berserk and destroyed T-Mat, two men in the process. Phipps was injured and Osgood ran outside without a protective suit. His body is still out there.

Kelly buys this story, despite the absurdity of it and she begins work on the system. Fewsham switches off the emergency link, ostensibly to conserve it, but really because he was ordered to by the warriors.

The warriors, however, are more worried about the elusive Phipps at the moment. He must be found so that he does not jeopardise their plans. The search begins anew.

With his weapon in place, Phipps turns his attention to contacting Earth. There is a small radio set in the store room. He links it to the solar power line, disconnecting the solar weapon for the time being, and tries to get a message out. No response. He sets about trying to boost the signal.

On the rocket, radio problems are plaguing the crew as well. All circuits are blown and they cannot contact Earth. Zoe thinks it doesn't matter now as they are nearly at the end of their journey. All they need to worry about is the homing signal from the moon. It is independent of T-Mat and remote activated from the rocket. They'll home in on it and use it to land.

To their great joy, the signal activates smoothly. They're nearly home free... as long as the signal holds.

Phipps continues to try and radio Earth with no luck. However, in his zeal, he has raised his voice and drawn the attention of a passing warrior. It enters the store room, unseen by Phipps until it is nearly too late. Phipps leaps to the solar power panel and switches plugs from the radio to the heat weapon. He throws the switch and vaporises the warrior with an intense burst of light.

Breathing a sigh of relief, Phipps plugs the radio back in and continues his attempts to reach Earth. Little does he know that his tampering with the solar power system has knocked out the rocket homing signal. It has cut out completely!

On the moonbase, Phipps is unaware of the predicament of his would-be rescuers. He readjusts his radio and resumes his attempts to contact Earth.

In the face of their impending death, Zoe retreats into the comfort of mental work. She calculates that at their present rate of drift, they will fly into the sun in approximately five weeks. Jamie is somewhat relieved that he'll never have to experience this. He reminds them grimly that they only have enough food and water for three days. Their deaths will be much more mundane than flying into the sun.

A few moments later, the Doctor is surprised to pick up a new signal on his headset - a signal from the moon. It is Phipps, still trying to reach Earth. Phipps is equally surprised to get a response, but downright shocked to discover that he is speaking to astronauts in a rocket coming to help him. Phipps recovers himself and reports the emergency: aliens have invaded the moonbase!

Meanwhile, Miss Kelly and her men have completed their repairs to T-Mat. The system is once again fully operational. Fewsham seems more nervous than ever. Kelly is ready to return to Earth but she is stopped by Slaar, leader of the alien invaders. They are soon surrounded by warriors. Both of Kelly's technicians panic in the face of the terrifying aliens and try to flee. Both are gunned down.

Slaar and his warriors surround Kelly, warning her to stay where she is.

Back on Earth, Commander Radnor gets an update from Kelly's assistant Brent. No word yet from moonbase. As soon as Kelly left, the emergency link switched off. Brent is certain she'll sort out the problem. Radnor is not so optimistic.

On board the rocket, the Doctor waits pensively through another orbit. They are out of range of Phipps' transmitter for most of the orbit. There are still a few seconds left until they are in range again. The Doctor can only hope that Phipps has managed to hold out against the Ice Warriors in that time. He and Jamie are sure from Phipps' description that it is the Ice Warriors who've invaded. They tell Zoe all they know of the Martian reptiles. The Doctor is certain they intend to take over the Earth as Mars is a dying planet. He wonders though how the cold-adapted creatures intend to make Earth their new home.

The rocket returns to Phipps' range and contact is re-established. They are all glad he's still alive. They need his help to make a landing on the moon. Phipps thinks it's too dangerous for them to come here, but there is no other choice for them. Zoe suggests adapting the rocket's homing equipment to follow Phipps' radio signal, replacing the automated landing signal. If he can keep transmitting, he can guide them in. Phipps agrees to try, but he warns them that the equipment he's using may not be up to the task.

A short time later, the Doctor has completed modifications and soon a steady bleeping fills the capsule - Phipps' signal. Zoe has computed the approach trajectory and they have only 17.5 seconds until they need to fire their retro rockets.

The crew take up landing positions and activate the rockets. The ship halts its forward motion and begins to descend, bottom first, toward the moon's surface. Zoe hopes they have enough fuel for a soft landing, Jamie hopes the homing beam doesn't conk out again, and the Doctor just crosses his fingers.

Phipps receives a message that the rocket is coming in for a landing and once again he is urged to keep transmitting. Suddenly a lighted tube on the radio flickers and dies. He is no longer transmitting!

The Doctor struggles to try and land the rocket on his own without the signal. There is no time to try and boost back into orbit. Zoe, knowing the difficulties full well, is horrified.

Phipps hurriedly replaces the tube and starts transmitting again. The signal returns to the capsule and the Doctor hurries to lock back onto it. He is successful and the rocket lands - rather bumpily - at the docking section of the moonbase.

The Doctor, Jamie, and Zoe are tossed about the cabin by the rough landing but are very glad to be down at last. But there is no time to lose. The Doctor directs Zoe and Jamie to see to refueling the rocket whilst he goes to find Phipps, following the map given to him by Radnor. It should be easy enough to reach the solar energy stores.

Zoe instructs Jamie on the automated refueling system, showing him the fuel gauge and telling him to switch the system off once it's full. Meanwhile, she is going to have a look at the rocket motors. She didn't like the sound of that landing and worries that some damage may have been done. Her concern about their ability to take off again worries Jamie.

Under Slaar's direction, Fewsham reactivates the worldwide T-Mat system. Connections are re-established with every city on Earth. Kelly cannot believe Fewsham is cooperating with the invaders, but he swears he is only doing it to save their lives. Kelly worries more about the other people on Earth and demands to know why Slaar wants control of T-Mat. She believes it has to do with armed conquest and tell shim he'll never succeed against the combined might of humanity. Slaar is once again calm and assured when he tells her there will be no resistance at all.

Kelly bravely refuses to help his plan in any way. Slaar promises that she will either assist or die.

The Doctor makes his way cautiously through the base and to the solar energy stores where he finds a very frightened Phipps. Phipps is very glad to have some company, but he is somewhat concerned by the Doctor's boldness. He doesn't seem to be afraid of the warriors, despite their murderous rays. In fact, he decides that he must oppose them and quickly. The Doctor says that they must destroy T-Mat in order to stop the warriors.

The Doctor reports his plans to Jamie in the rocket via radio. Jamie is also a bit put out with the Doctor's boldness but accepts the plan and signs off. When Zoe returns, Jamie tells her that they should prepare the rocket for takeoff. The Doctor will return with Phipps as soon as they've put T-Mat out of action. Zoe is horrified. Her suspicions were confirmed and the rocket motors are useless, damaged in the landing. The only way back to Earth is by T-Mat. They must stop the Doctor!

Unable to reach him by radio, Jamie and Zoe race out into the base to try and find him.

The Doctor and Phipps make their way toward the control room. They stop for a moment to get their bearings and the Doctor sees an Ice Warrior coming down the corridor toward them. He is stunned to see Miss Kelly in the creature's grip. How did she get here? So shocked is the Doctor that he does not get out of sight. The warrior sees them and the chase is on.

Kelly slips free of the creature and vanishes into the corridor as well. She, Phipps and the Doctor do their best to evade the warrior, but there are soon more of them in the chase. The Doctor is eventually cornered by two of the creatures when he runs into a locked door. They bear down on him, ready for the kill.

The Doctor thinks fast and tells the warriors they can't kill him. They have no orders to do so and he promises to be useful to them. The arguments don't seem to be working, that is until the Doctor professes himself to be a genius. He is conducted away by the warriors, out of the frying pan and into the fire.

Zoe and Jamie also traverse the corridors, but without any real direction. Zoe did not get a good enough look at the map to memorise it properly and they are now lost. They are forced to flee when a warrior spots them, but they manage to evade it. Zoe now realises the Doctor and Jamie weren't exaggerating about the nightmarish creatures. They resume their efforts to find the Doctor or the solar energy room.

Slaar prepares the next phase of his plan and tells Fewsham that he will soon be made to dispatch a cargo to selected cities via T-Mat. However, he's interrupted by the arrival of the Doctor and his guards. The warriors are sent out to recapture Kelly whilst Slaar interrogates the Doctor.

Fewsham says that the Doctor is not a member of the moonbase crew, but Slaar does not believe the Doctor arrived here by rocket. The Doctor remains defiant, insisting that he not only came by rocket but that the Earth has a whole fleet of rockets ready to come here and defeat the warriors. He is banking on creating some paranoia in Slaar's mind.

The Doctor turns the tables, asking questions himself and trying to determine Slaar's plans. It can't be invasion by force as there are too few warriors here to overcome Earth's defences. The answer comes when two warriors arrive in the control room. They are bearing a large casket containing "seeds". Slaar is ordered to contact the Martian Grand Marshall for final instructions. He does so, leaving his warriors to guard the Doctor and a disconsolate Fewsham. Any attempt to escape will result in death.

The Doctor sidles over to speak to Fewsham but is unimpressed by the little man's rationalization of his collaboration with the invaders. Fewsham doesn't know what's in the casket but he supposes it is the "cargo" he is to send to Earth. The Doctor is determined to find out what it is - and determined that Fewsham is going to help him.

Jamie and Zoe have met up with Phipps and Kelly in the solar stores. They learn of the Doctor's capture. Phipps tells them all of the booby trap he rigged up to kill the warriors. Zoe remembers the Doctor telling her that the warriors can't stand heat. Phipps suggests turning up the head in the entire base, however the controls for temperature are in the control room and there are warriors roaming the corridors.

Phipps remembers the maintenance tunnels that run throughout the base and sets about opening the hatch in the storeroom. The plan is to turn up the heat, knock out the warriors, rescue the Doctor, and T-Mat back to Earth. But they'd better hurry. There's no telling how much time the Doctor has in the hands of the Ice Warriors.

Fewsham resists helping the Doctor, sure his plan will fail and they'll be killed. However, when it becomes clear that the Doctor will act without him, Fewsham relents. At least this way, they may stand a chance. He crosses the room, saying he needs to check some equipment, whilst the Doctor moves carefully toward the casket. Unfortunately, the warrior on guard doesn't buy Fewsham's story and orders him back to his seat. The weak-willed little man gives in and the Doctor is caught.

Slaar returns at this moment and stops his warrior killing the Doctor. Incredibly, he orders the Doctor to open the casket. Inside are several smooth round white pods, like seeds. The Doctor picks one up and suddenly it expands in his hand, swelling like a balloon. It explodes before him, scattering a cloud of fine particles. The Doctor gags and collapses, motionless on the floor.

Fewsham is shocked, certain the Doctor is dead.

In the solar stores, Jamie and Phipps struggle with the disused cover on the maintenance tunnel. It won't budge. Suddenly Zoe shouts a warning. She's spotted a warrior in the corridor. It lumbers toward the storeroom. There is no place to escape. Jamie wedges a metal bar into the door, but that doesn't stop the mighty warrior for long.

With the help of Kelly and Zoe, Phipps reattaches all the cables to his heat booby trap, finishing just as the warrior bursts in. As before, the intense heat and light vaporises the creature before them. They are safe once again.

In the control room, Slaar is ready to proceed with the next phase of the plan. Fewsham is dispatch one of the seeds to Earth. He spares a moment to look at the Doctor's motionless body, reminding himself of how ruthless the warriors are. Meekly, he does as he is told.

At T-Mat Earth Control, Radnor - along with Professor Eldred - receives a report on the worldwide chaos caused by the loss of T-Mat. Food shortages are widespread, despite the reversion to primitive ground transport, and it will only get worse. Radnor's black mood becomes blacker still.

A short time later, the Martian seed pod arrives in the T-Mat cubicle, accompanied by the usual arrival signal. Radnor, Eldred, and Brent approach. They are pleased that Kelly has apparently repaired the damage to the system, but are mystified as to what the object might be.

Chaos erupts in T-Mat control as the Martian seed pod explodes, spewing a toxic cloud of smoke. Brent is overcome as the Doctor was and collapses, dead. Eldred and Radnor cough violently until Eldred suggests expelling the smoke via the air conditioning system. A guard complies with the order and the smoke is sucked out of the building.

When the air clears, Radnor has Brent's body removed for immediate autopsy. They must figure out what killed him. Eldred looks at the pod, which has now shriveled up. Both of them concur it is like some sort of plant pod, Eldred going so far as to liken its explosion to that of a plant spreading its seeds. And now the unknown smoke-like substance emitted by this pod has been expelled into the air of London.

More of the seed pods are despatched from the moonbase by Fewsham, acting under Slaar's orders. Ottawa. Oslo. More and more. Fewsham does as he is told, denying in his mind the true enormity of his collaboration. Slaar will not tell him why he is doing this; he only orders the despatches continued.

In the solar energy storeroom, Kelly works to repair one of the reflectors used against the Ice Warriors. It burnt out on its last use. Zoe assists. Jamie and Phipps are now gone into the maintenance tunnels, their goal is to reach the control room and turn up the heat. They clearly haven't succeeded yet and Kelly thinks it unlikely they've even reached the control room yet. And even when they do, there's still the warriors to contend with...

Phipps leads Jamie through the narrow passages and eventually they reach the control room. Through the various grilles, they can see Fewsham doing the warriors' bidding, dispatching the pods via T-Mat. They have no idea what is going on, more can they see any sign of the Doctor yet.

Commander Radnor receives reports of more seed pods arriving in T-Mat cubicles all over the world. Most recently, New York, where two men were killed instantly just like Brent. That makes four deaths in sixteen arrivals. Radnor is concerned, but Eldred's worries are much larger. He is certain those pods weren't sent to kill just a few people at random, they were sent for a larger purpose. If only he could discern some pattern in the arrivals.

The autopsy report on Brent arrives with an astounding finding: he died of oxygen starvation. Somehow a means of death that normally takes several minutes occurred instantly due to this seed pod and the smoke it emitted. Now that toxic smoke is mingling with the air of London. Eldred hopes that this will serve to dilute the smoke, but his tone suggests he fears otherwise.

In fact, it is not. If anything, the smoke is thicker now as it drifts over the city. On the grassy grounds of T-Mat Control, a new pod grows from a lump of foam on the ground. It expands and explodes, added even more of the smoke-like substance to the thickening cloud.

On the moon, Fewsham is relieved to come to the end of his task. This is the last of the seeds, although Slaar says more may be needed. Fewsham goes to check on the Doctor, whose body lies neglected on the floor. To Slaar's surprise, the Doctor is still alive. Most humans would be dead after breathing in the seeds. No matter, though. He wants the Doctor kills and he has an ingenious way of doing it. He orders Fewsham to place the Doctor into a T-Mat cubicle. Not knowing the reason, he does so.

Slaar then orders Fewsham to adjust the T-Mat controls and transmit the Doctor into space between the moon and Earth. Fewsham is horrified anew. In the maintenance tunnel, Jamie and Phipps overhear all of this and act quickly to save the Doctor, crawling toward the back of the T-Mat cubicle.

Fewsham protests the barbarous act he is being asked to perform. Even more coldly, Slaar tells him that by sending the seeds to Earth, he has already murdered the entire human race. What's one more person. Something inside Fewsham snaps. He had been trying to deny this reality since he started helping the warriors, but he can no longer do so. Genocide. He refuses to cooperate any further, but his resolve is weak. He does not want to die and so sets about reprogramming the T-Mat controls.

Whilst he does this, Phipps and Jamie struggle with the inspection hatch leading from the maintenance tunnel to the back of the T-Mat cubicle. They are racing against time to get the Doctor out. Luckily for them, Fewsham stalls, trying to put off this evil inevitability.

Finally, with no other choice, Fewsham activates the switch. When he turns and sees the cubicle empty, he cries out in helpless horror. The Doctor is dead, suspended in space with no pressure suit. He blames Slaar, but it was his own hand that did the deed. He will never be able to forget that.

It is now tie for the next phase of Slaar's plan. He orders Fewsham to reset the T-Mat controls to transmit one of his warriors to London. Fewsham drags himself up and starts to do so.

Little does the despondent Fewsham know that the Doctor is still alive, safely in the maintenance tunnel with his friends. Jamie sets about carrying the unconscious Doctor back to the solar stores whilst Phipps returns to his attempt to reach the base's heating controls. He circles round to the other side of the control room where he can clearly see the heating controls, high up on a catwalk at one end of the room. However, the hatch there proves too small for him to fit through.

Back on Earth, there are more seed pods than ever now, growing almost anywhere the smoke drifts. Mountains of foam cover every patch of open ground, swamping all the vegetation.

Reports of widespread vegetable blight due to the seeds and foam are relayed to Radnor and Eldred at T-Mat Earth Control. However, they have no time to pay attention. Suddenly an armoured reptilian giant materialises in a T-Mat cubicle and smashes its way out. The two men are horrified by the creature. It kills every guard in its way as it heads for the exit. It clearly has a mission and will let nothing stand in its way.

On the moon, Slaar leaves the control room, his work done for now. One warrior is left on guard over Fewsham, the others are despatched to find and capture the fugitive humans once and for all.

In the solar stores, Kelly tends to the Doctor, whom she thinks will recover in time. Jamie is ready to try again for the heating controls, but the newly-returned Phipps says they're impossible to reach. Zoe, however, is certain she can fit through the narrow opening, being much smaller than any of the others, but Jamie refuses to let her go. He says it's too dangerous for her. An order form Kelly, however, and the matter is settled. Zoe is their only choice and they'd better hop to it.

On the grounds of Earth Control, the warrior strides through oceans of foam, undeterred by anything in its path. Professor Eldred has realised that this creature is connected to the seed fungus. He can only wonder what its plan might be.

The creatures encounters a group of men attempting to combat the foam/fungus with chemicals. They are having little luck and are forced steadily back. But the worst is yet to come when the warrior approaches. It wastes no time in killing all 3 men, stopping only for a second to do so. Then it is off again.

The deaths are reported to Radnor and Eldred. They still cannot fathom where the warrior is heading, but at least they know where it is at the moment.

Phipps leads Zoe through the maintenance tunnels but seems unsure of the route this time. He is starting to panic, the stress of events working on his nerves. Zoe has to work quickly to shush the man when he starts shouting, then suggests a sort rest to try and calm him down.

Radnor receives a direct reports from a security guard in the eastern part of the T-Mat complex. He has sighted the creature and is observing him from behind a tree. Unfortunately, the creature turns and sees him, staring directly at him. The guard's nerve cracks and he tries to run. He is shot down by the warrior's sonic gun. The warrior moves off.

Transmission ceases and Radnor knows why. He orders more guards to the east compound, even though he knows it will do no good. Eldred fears that more creatures are to come in all the cities affected by the seed pods. As he looks at the map of those cities, it finally occurs to him what the connection is - all of them are in the Northern Hemisphere, where it is winter. No seeds have appeared in any warm climate area. Why not?

A computer report comes through reporting widespread social breakdown due to the loss of T-Mat. All emergency measures are proving inadequate. Radnor shuts off the report, unable to listen to any more. He knows that many are going to die. Millions, perhaps. Eldred fears that most of the world's population may die, not from starvation but from alien invasion. He is certain that more of these warriors are on the way.

Right now, one is enough to cause problems in London. In continues on its unswerving path.

Back on moonbase, Jamie is worried about Zoe and Phipps. They have been gone a long time and the temperature is still normal. Kelly holds Jamie back from going after them. They must stay put here. He is glad to know that she has repaired the solar heat weapon, but he still wonders what's keeping Zoe and Phipps.

The rest it seems has not helped Phipps. He is still unable to remember the way to main control. Zoe tries hard to remember the map the Doctor showed her and despite Phipps' pessimism, she chooses a direction and strikes out.

Luckily, she is right and moments later they reach the control room. Unfortunately, the warrior on guard is direction in view of the maintenance hatch. They daren't make a move until it does.

Kelly is nearly ready to allow Jamie to go after the others when suddenly there is a noise outside the storeroom. A warrior comes in to search. Jamie and Kelly hide, ready to use their weapon. To their horror, it does not work. Kelly's repair of the equipment has been unsuccessful. The creature somehow does not see Jamie and Kelly in their hiding places, but it does see the Doctor, lying on a table in the centre of the room. It moves toward him.

In the control room, Fewsham is exhausted and starving. He begs the guard for food and rest. This distraction is enough to allow Zoe and Phipps to remove the maintenance grille. Fewsham sees this and hurriedly moves to further distract the guard. His sudden selflessness is surprising, even to him. He moves to the T-Mat cubicle to "check it". The guard follows.

Zoe scrambles out and moves cautiously to the catwalk and the heating controls. She must cross a wide expanse of open area and then struggle with the stubborn wheel that controls the temperature. Phipps watches nervously as she finally manages to move the control to "full on". The temperature begins rising almost immediately.

Trapped in the line of fire, Zoe begs Fewsham to help her. After a moment's hesitation, he acts, attacking the warrior. It is a futile effort as the mighty creature easily swats him away. However, the delay is enough. As the temperature rises, the warrior begins to stagger for breath. A moment later, it falls unconscious on the floor. Zoe is safe.

She leaps down from the catwalk and helps the battered Fewsham up. She is grateful for his help, but cannot understand why he did it. She was sure he was willingly collaborating with the warriors. Fewsham is distraught by this revelation, insisting he was only trying to save his life. He tells Zoe that Slaar and the rest of his warriors are back at their ship. She heads back to the solar stores to fetch the others, using the maintenance tunnel for safety. With luck, they can all escape to Earth by T-Mat before Slaar returns.

In the store room, Jamie and Kelly still hide from the warrior. It seems to have lost interest in the Doctor...until he begins to stir. The creature turns again and comes back. Jamie, desperate, attacks the creature, as does Kelly. Both are knocked away. But just as the warrior aims its sonic gun, the rising heat takes effect and it collapses. They are all safe.

The Doctor gets to his feet, seemingly little worse for the effects of the toxic smoke he inhaled. He is concerned about the heat and Jamie explains. At that moment, Zoe returns, glad to see the Doctor alive and well. She reports Phipps' death and Fewsham's apparent change of heart. But that matters little at the moment - if they can escape via T-Mat, then there's no time to lose. They race for the control room.

Back on Earth, a bad situation gets worse for Commander Radnor. Not only does he have to deal with fungus, crop blight, and a marauding alien warrior, he now has to deal with Sir James Gregson, UN plenipotentiary in charge of T-Mat. He is clearly the "man in charge" and begins firing questions at Radnor immediately upon arrival. Radnor recaps a confusing situation, including the rocket, the short-term repair of T-Mat that allowed Miss Kelly to get to the moon, and the lack of any contact with moonbase despite these efforts. Gregson's tone is dubious and dismissive.

Radnor starts to explain the theoretical connection between the T-Mat breakdown, the seed pods, and the creature, but Gregson turns to Eldred for answers instead. He simply wants to know where the monster is. Eldred shows him a map of the T-Mat complex. The warrior was last sighted near the Weather Control Bureau, which shares the complex.

Indeed the creature has waded through the foam to the very door of the weather station and straight inside. It has achieved its destination. Inside the station, there is only one technician on duty. He is shocked by the appearance of the alien warrior and tries to run. He does not get far before he is gunned down.

Scanning all the equipment, the warrior finally finds the unit it wants. On it are four levels marked "dry". It activates all 4 levers and then turns its gun on the machinery, welding the levers in the "dry" position. Mission accomplished.

On the moonbase, Fewsham begs Miss Kelly to understand why he had to help the warriors. She seems unmoved and promises there will be a time for an official inquiry later, back on Earth. They must leave immediately. Fewsham says he will dispatch the others and then use the system's time delay switch to send himself. The Doctor doesn't stay and argue, herding his companions into the cubicle. However, Kelly recalls the time delay circuit as being listed as out of order on a previous report. Fewsham says it is fixed now as he despatches the Doctor, Jamie and Zoe.

Once they are gone, Kelly goes into the cubicle. She is a bit reluctant as she fears that Fewsham is up to something, but she goes. She arrives at Earth Control just behind the others, much to the surprise of Radnor. He, Gregson, and Eldred are full of questions and concerns and pelt the group with questions. It does not surprise the Doctor to learn that an Ice Warrior is here on Earth.

Miss Kelly reports that all of the moonbase crew are dead at the hands of the warriors, all except Fewsham. This leads them all to wonder what's keeping him. Kelly investigates the equipment and discovers that the time delay switch is indeed still out of order. Fewsham knew it and lied. She thinks it's because he really is in league with Slaar, but the Doctor thinks there may be another reason.

Fewsham waits in the control room, an unreadable expression on his face. For some reason, he has chosen to stay behind. When he hears Slaar coming, he slumps at the control panel, pretending to be unconscious. Slaar stumbles into the control room, fighting the effects of the oppressive heat. His breathing is laboured and every step is difficult. Somehow he finds the strength to climb up on the catwalk and reach the heating controls, turning them back down. As the temperature cools, Slaar regains himself and addresses Fewsham.

Fewsham acts as if he's been beaten and says the others did it. They snuck in through the grille, turned up the heat, and escaped via T-Mat. He says he refused to go with them as he knew that he would be executed as a traitor on Earth. As expected, Slaar is pleased with this. He vows that Fewsham's life will be spared, as long as he continues to cooperate.

The next phase of the plan is the arrival of the Martian invasion fleet here on the moon. Once the seeds have done their work, then it will be time to invade Earth.

The Doctor confirms for Radnor, Eldred, and Gregson that the warrior, the fungus, and T-Mat are all part of the same plan. He's not sure what yet, but he hopes that by analyzing a sample of the crop-destroying fungus that he might learn something. He and Eldred set off to collect a sample. Radnor warns him about the exploding pods, unaware that the Doctor has ample experience in the matter.

Zoe puzzles over Fewsham's decision to stay on the moon, not convinced of Kelly's explanation that he feared an inquiry. However, Kelly has little time for idle speculation. She is trying to find a way to get T-Mat working again, independent of the moon and controlled from Earth. When an idea occurs, she goes off to talk to Radnor, leaving Zoe and Jamie to speculate on the Doctor's plans to get a sample of the fungus.

And they are right to be worried. In the gardens of T-Mat Control, the Doctor carefully wades in to get a sample. So intent is he on his task that he doesn't see a pod swelling at his feet. It explodes and he scampers away, coughing violently. Abandoning caution, he covers his face with a handkerchief and simply scoops up a giant mass of the stuff before running off.

Kelly's idea is greeted with guarded enthusiasm by Radnor and Gregson. She has suggested using a communications satellite as a relay for T-Mat instead of using the moon. It would mean less capacity, but vital food and supplies could get through. Zoe and Jamie are confused as it sounds like they are talking about launching a rocket, but Kelly tells them that satellite launches are still routine, just not manned rockets. Kelly appeals to Radnor and Gregson to put her project on the fast track.

The Doctor and Eldred work together to analyse the foam. It is definitely organic and definitely a fungus designed to absorb oxygen. A blanket of the stuff would reduce the oxygen content of Earth's atmosphere to 1/20 normal. The planet would be uninhabitable for human begins, but would be perfect for the Martian warriors. As they talk, the specimen on the table becomes active, rising up from the container. Even without vegetation to feed on, the stuff is active.

Suddenly a new pod appears in the foam, swelling ready to burst. Eldred is ready to run but the Doctor decides to try and stop it, despite his fear. He throws everything he can find at it, including sulfuric and hydrochloric acid. These don't work, but the last liquid he tries does work. The pod shrinks and eventually disappears. He's found the answer.

The Doctor calls in to T-Mat Control, interrupting Jamie and Zoe's speculations on the warrior's mission here. He reports joyously on his findings: ordinary water destroys the fungus and the seed pods! Radnor, Kelly, and Gregson, however, are in conference so the Doctor relays his instructions to Zoe. They must reach the Weather Control Bureau and tell them to make it rain as much as possible. He himself has tried to reach them by video phone but has gotten no answer. He and Eldred will return to control shortly.

Zoe uses the computer to try and relay this message to Radnor, but he is unavailable and the computer will not take the message. Zoe and Jamie will just have to go to the weather station on their own, unaware that the Ice Warrior has already been there.

On the moon, the warriors bring the communications unit from their ship into the control room and order Fewsham to connect it to the solar battery. He insists he cannot do so unless he knows its purpose and learns that it is for projecting a homing signal to their invasion fleet and to guide them to the moon. Slaar will tell him nothing more and orders him to connect it.

Zoe and Jamie reach the weather station, skirting round the rising tide of fungus to get to the door. They close and lock the door once inside, hoping to keep both the foam and the marauding warrior outside. They pass through the silent and empty corridors to find the main control room. There they find the dead technician and they know why the Doctor couldn't reach them by video phone.

What's worse, the machinery has been damaged, locking the rainmaking equipment to the "dry" mode. The warrior has already been here. Suddenly they hear the hissing rasp. It is still here and Jamie and Zoe race to conceal themselves, hoping the creature won't come looking.

The Martian Grand Marshall learns from Slaar that all phases of the plan are in motion. The fleet is now approaching the moon and awaits Slaar's homing signal. As the two warriors speak via the communications unit, Fewsham moves slowly and carefully to the control panel and activates the video link with Earth.

Back at T-Mat Earth Control, the launch preparations for the communications satellite is underway, nearly ready for liftoff. Kelly and Radnor apparently sold Gregson on the idea and his clout has made it come to fruition very quickly indeed. The Doctor and Professor Eldred return to T-Mat Control just as the video link with the moon switches on. They watch in fascination as Fewsham addresses Slaar.

He asks to test the homing beam, to make sure it pulses at the proper rate before being activated for the fleet. Slaar is somewhat suspicious of this request but agrees to it. It makes sense to be thorough.

Realising what he is watching, the Doctor orders the incoming transmission to be recorded. Radnor complies, unsure why.

The signal commences and after a few seconds, Slaar is satisfied and ready to turn it off. Fewsham nervously asks for it to continue whilst he re-checks the connections. He is stalling, hoping that someone on Earth is listening. He natters to keep his nerves in check, but his words are meant to communicate with his comrades on Earth. If anything should go wrong with the signal, the alien fleet would overshoot the moon. With the fleet at marginal fuel levels, it would mean the end of them as they will be drawn into the sun. He doesn't know how, but he hopes that Kelly and the others will be able to do just that with the information he is providing.

After a moment more of listening to this chatter, Slaar realises his plan and reacts. He sees the active video link and knows that Fewsham has betrayed them. The nervous little man is defiant to the last. He has managed to use his position of trust with the warriors to send their plan to Earth. He can only hope as he is gunned down by a warrior that he has been able to redeem himself and save humanity from the terror he helped unleash.

Slaar has the video camera destroyed and the link is cut. All on Earth are saddened by the death, but the Doctor doesn't waste his grief. He orders the imminent satellite launch halted. Because Fewsham risked his life to allow them to overhear and record the Martian homing signal, they now have the means to stop the alien invasion fleet. If they can launch their own version of the signal, transmitted from the satellite, they can redirect the fleet away from the moon and into the sun. Radnor halts the launch, hoping that they now have a chance at victory.

Radnor, however, is still concerned about the fungus. The Doctor is stunned to learn that Zoe and Jamie never delivered his message about the water and the need to make rain. They must have been unable to reach Radnor in his conference. The Doctor, knowing his companions well, is sure that they would have gone to the Weather Control Bureau themselves in that case - it was too important to wait. But that brings up a much more pressing problem: Eldred tells him that that warrior was last seen near the weather station!

The Doctor races off to try and help them. He reaches the building without much trouble, but the deadly foam is all around the place, even up to the door. He covers his face with his handkerchief and wades in. He reaches the door but it is locked tight. He pounds on the door, trying to get some response, all the while keeping a wary eye on the foam surging around him. There is no answer and he becomes a bit desperate, pounding again and calling out to Zoe and Jamie.

The sounds carry to the control room and the warrior hears it. Luckily, this breaks it off from his survey of the control room - where it would most likely have found Zoe and Jamie - and it moves off toward the door.

Afraid that no one has heard him, the Doctor decides to try and find another way in. He moves off away from the door but is blocked by a giant wall of foam. He turns back to the door but slips and falls under the foam. He is back on his feet quickly, sputtering and coughing, but he knows he is trapped for certain now. He must get inside and so resumes pounding.

The warrior heads for the door, followed by Jamie and Zoe. Jamie darts out before the warrior to distract it, racing off into the interior of the station. Luckily, the creature takes the bait and follows Jamie into the corridors, firing its weapon as it goes. Zoe goes to the door but to her horror cannot make the locking mechanism turn.

Zoe manages to force the door open just in time. The Doctor falls, in, followed by a surge of foam that nearly buries both of them. Together they close the door, blocking out the rest of the stuff. The Doctor looks like a foam-covered drowned rat, but he is otherwise unharmed. He learns of the Ice Warrior loose in the building and they both race off to help Jamie.

Jamie is nearly cornered in the control room by the marauding warrior, but he manages to evade its sonic gun. He escapes down a corridor, closing a door behind him. At least that will delay the warrior. Luckily, he runs straight into the Doctor and Zoe. All three race for safety as they hear the warrior blast through the control room door.

The Doctor and his friends reach a solar energy equipment store room and decide to hide out in there. The Doctor, it seems, has an idea. Despite Jamie's "assistance", the Doctor manages to close the radiationdoor just ahead of the warrior's arrival. It should hold for at least a little while against the sonic attack.

Zoe recalls the heat device that Phipps rigged up on the moonbase and wonders if they can do the same thing here. Excitedly, the Doctor scours the equipment stores, thinking it a very good plan.

Meanwhile, a group of security guards bearing water tanks makes its way to the weather station. The fungus retreats before them. They enter the building, guns at the ready.

The warrior hears the commotion and breaks off its attack on the storeroom door to go and face the newcomers. The guards are not prepared for the creature they see before them. Two are killed instantly. The others scatter.

The Doctor completes his heat projection weapon even as the sounds of gunfire ring out through the station. All of them know the guards don't stand a chance against the warrior. Now ready, the Doctor orders Jamie to open the door. Unfortunately, the warrior is not there, drawn off by the guards. The Doctor is saddened that he wasn't quick enough to stop the warrior. Now he'll have to take the weapon to the warrior. He and his companions set about hooking the solar projectors to lengths of HD cable.

The remaining guards are forced out of the building, their guns proven useless against the armoured warrior. Even a point-blank shot to the head does nothing. One more guard is killed, his body lost in the foam.

The Doctor moves cautiously out of the storeroom, projectors in hand. Jamie and Zoe stand by to throw the power switch. A tense moment later, the Doctor is face-to-face with the warrior. At his shouted order, Zoe activates the device. As on the moon, the intense heat and light vaporises the creature on the spot. They are safe.

Just as Commander Radnor is about to give up hope, he receives a call from the Doctor, saying that all is well. Both men are concerned over the damaged the warrior may have caused in the weather station and the Doctor goes off to check it after learning that Professor Eldred and Miss Kelly are hard at work on duplicating the warriors' homing signal.

Their initial test yields a signal too high and fast. Miss Kelly tinkers with the frequency and after a moment, the signal is pitch perfect. Eldred wonders how the transmitter will get to the launch pad without T-Mat, but Kelly has already thought of that. She's found an old petrol car in a motor museum that still functions. It's crude, but it will work. Eldred is impressed.

Radnor says the car should be able to get through the foam by use of water hoses, but the worldwide problem of the fungus still remains. The only way to eliminate it is if the Doctor can make it rain.

At the weather station, the Doctor is tackling that problem at this very minute. He is pleased to see that only the control levers on the rain-making equipment are damaged. The workings are unharmed. Borrowing Jamie's dirk, the Doctor pops open a panel in the unit and extracts a mass of wires. It's just a matter of sorting out what wire does what job. Simple!

On the moonbase, Slaar is being chastised by the Grand Marshall for killing Fewsham. His technical expertise was needed to operate T-Mat. Slaar has a vague plan to operate the equipment himself and use it to fetch another technician from Earth but the Grand Marshall is unimpressed. Slaar is ordered to procure another human immediately. At least the homing signal is working well. The fleet is headed for the moon. Meanwhile, Slaar goes back to his ship to finalise the invasion plans.

The Doctor, through trial and error, succeeds in reconnecting one of the rain circuits. Jamie is sceptical as he can clearly see that it's not raining outside, but the Doctor tells him that weather control is a difficult technology. Results will not be instantaneous.

The Doctor then reveals that he has another little job to do. His companions are worried as it involves making some alterations to his heat weapon. What on Earth for?

Meanwhile, the communications satellite launch completes its countdown and the rocket streaks toward the sky. Eldred is awed as always by the sight. The Doctor, Jamie, and Zoe return to T-Mat Control with news of the impending rain. The Doctor has completed his alterations to the solar energy weapon, rendering it portable. The power pack rests on his back and the reflectors are now hand-held, connected by a mass of wires. He has done this to ensure that their fake homing signal succeeds in drawing off the Ice Warriors. To do this, it is necessary to put the real signal out of action. As soon as the satellite is up and ready to transmit, the Doctor plans to T-Mat himself to the moon and stop the real signal. His portable heat weapon will hopefully help him deal with any warriors he may face at the moonbase.

It is not long before orbit is achieved and the satellite's signal is ready to be broadcast. Miss Kelly picks up the real signal being transmitted from the moon and it is now time for the Doctor to go into action. As soon as he succeeds in stopping the real signal, Kelly must activate hers.

Zoe urges the Doctor to be careful on this dangerous mission and he tries to reassure her. The Doctor's trip will be the first test of Earth control of T-Mat via satellite. Luckily, it works perfectly. A split second later, he appears on the moon.

He sneaks out of the cubicle to find just one warrior on guard in the control room, its back to him. By the time it turns, the Doctor has his weapon ready and it works perfectly, vaporising the warrior. The Doctor shrugs out of his weapon and moves to the alien communications device, flipping switches and trying to get the top open. The homing signal is still audible in the control room.

The Doctor is interrupted by Slaar and a warrior and has no time to reach his weapon. Slaar stops his warrior from killing the Doctor but does make sure the solar weapon is destroyed. Slaar is somewhat surprised to see the Doctor still alive, but actually seems glad of it. He still needs human assistance.

Slaar takes a moment to check the communications device. The sound of the homing signal still fills the control room and all appears normal. The Doctor says ruefully that Slaar entered too quickly for him to complete his task. Then Slaar turns his attention to the Doctor's usefulness. Under threat, the Doctor admits he knows a little something about the operation of T-Mat. Slaar will allow him to live as long as he is useful and cooperative. The Doctor is allowed to sit down at the controls under strict observation.

On Earth, Kelly reports that their false homing signal is now being beamed into space. She is convinced that the Doctor has succeeded as she is no longer registering the real signal. Eldred, however, is sceptical. Without word from the Doctor, they cannot know for certain that the real signal has been stopped, and there is still no sign of the Doctor. That fact worries Jamie and Zoe above all else.

The Grand Marshall reports to Slaar that the homing signal is being received. The fleet will soon enter the gravitational field of the moon. He is pleased to learn that Slaar has found another human to help in T-Matting their warriors to Earth and signs off. He will contact Slaar once landing is imminent. The Doctor remains defiant in the face of Slaar's plans for him, noting that anything could still go wrong with the landing. Slaar is equally confident, certain nothing will go wrong. And if it does, the Doctor will be the first to die!

At T-Mat Control, a tense crew watches on the scanner as the Martian fleet nears the moon. They still appear to be following the real signal, spelling failure for their plan. However, at the last second, the formation turns en masse, heading away from the moon. The Doctor's done it! The real signal is off and the ships are following the false signal straight into the sun.

Everyone is pleased, but Jamie's main concern is still the Doctor. Why hasn't he returned or contacted them? Radnor tells him to be patient; a squad of guards is on its way here, bringing flame throwers. As soon as they arrive, they'll be sent to the moonbase via T-Mat. However, Jamie is too impatient and will not wait. He pulls Zoe aside and tries to enlist her aid to T-Mat him to the moon. She is hesitant at first, but Jamie's argument is convincing. Either the Doctor is fine, in which case she needn't worry. Or else he's in trouble and needs Jamie's help.

On the moon, Slaar receives a desperate call from the Grand Marshall. The fleet has overshot the moon and they are now on course for the sun with insufficient fuel to escape. He says they are still receiving the homing signal loud and clear. Neither can figure out what is wrong but both know what this means: the destruction of their fleet and the deaths of all their warriors. The communication breaks up as the Grand Marshall blames Slaar for this massive defeat.

Slaar is livid. He checks the communicator and discovers that no power is reaching the homing signal and it all becomes clear. The Doctor lied and he was able to successfully sabotage the machine before he was caught. The Doctor owns up to it proudly. The signal that they can hear has gone no further than this room. He reveals the satellite and the false homing signal. Through his efforts, the invasion has been defeated. Slaar seems stunned that the Doctor could have condemned all those warriors to death, but the Doctor reminds him of the much wider genocide he and his warriors had planned. And when the Doctor reveals that the fungus has been defeated as well, Slaar loses control. The defeat has driven him mad.

Slaar orders his remaining warrior to kill the Doctor, but Jamie's timely arrival in the T-Mat cubicle distracts the creature. It turns toward Jamie but the Doctor leaps over the control console and deflects its aim. The blast hits Slaar and he is killed. Jamie leaps into the fray, jumping onto the warrior. The Doctor races to the solar power line and disconnects it. He warns Jamie away and touches the live lead to the warrior. It staggers and dies as the full power surges through it.

In one flash, the danger is averted and the last threat of the Ice Warriors is ended. The Doctor and Jamie, victorious against the creatures once again, prepare to return to Earth via T-Mat.

Back on Earth, a steady rain is falling all over the planet. With it comes some flooding, but that is a small price to pay as it dissolves away the deadly alien fungus. At T-Mat Control, Radnor and his team receive news of worldwide success against the fungus. Additionally, there are reports of relief from world food shortages due to the return of limited T-Mat service and a not of congratulations to Radnor from the UN Security Council.

Zoe admits that she wasn't exactly certain the Doctor knew what he was doing with the equipment at the weather station. The Doctor is chagrined but both are glad that she was wrong. Radnor fully appreciates the Doctor's help in ending the fungus threat. With that out of the way, he and Kelly can turn their attention to getting T-Mat fully operational again - this time controlled from Earth. An argument erupts when Professor Eldred insists that rockets be kept on permanent stand-by to supplement T-Mat. Kelly and Radnor are against the idea, despite recent events, and Eldred appeals to the Doctor to support him. However, the Doctor and his companions have quietly slipped away during the commotion.