In a lab, at the South Pole, three scientists named Stevenson, Moberley and Winlett reside. Charles Winlett is outside in the snow picking at the ice, the 9th layer of permafrost. He digs up an egg and his partner Derek Moberley discuss it but Moberley gets Winlett to get back to the large camp buildings. "Animal, vegetable, or mineral?" asks Moberley of botanist John Stevenson. It is vegetable but with skin hard as iron. It's been in the 9th layer for 20,000 years. Charles thinks it tropical. John tells them he feels something about the pod; Derek jokes it is the rice pudding he had for lunch. John thinks the pod is alive -- a living organism. Derek suggests coffee but Charles suggests an added bonus -- three handed crib. John will send pictures of the pod to London.

Back in London, sitting, the Doctor plays with his yo-yo in the World Ecology Bureau office of Richard Dunbar who doesn't think the Doctor can help them. Dunbar's boss Sir Colin Thackeray insists he show the Doctor photos of the pod. The Doctor tells him to sit down please and puts his own feet on Dunbar's desk. The Doctor suggests the pod came from outer space, and calls the pod a time bomb. Dunbar tells the Doctor that Colin Thackeray has a daily video link to the Antarctic Lab. The Doctor explains to him to warn the scientists there not to touch the pod. He informs a stunned Dunbar that he will go to the lab and has his toothbrush to prove that he is ready. After the Doctor leaves, Dunbar calls Sir Thackeray, "That chap you called in from UNIT, is he quite sane?"

John calls Charles into the examining room to notice the pod is growing. It has grown 5 centimetres since the morning. Ultraviolet radiation may be the key to how it has grown. London has called already to tell them not to touch the pod. John thinks the Doctor is going to turn out to be some old crank that Sir Colin dug out of retirement. The Doctor is due in tomorrow. John tells Charles it is their discovery.

Dunbar in London, arrives at the country home of millionaire Harrison Chase and is announced by the butler Hargreaves. Chase asks what the World Ecology Bureau is doing about the abuse of shrubs and trees via bonsai. Chase has thousands of plants and trees on his estate. Dunbar shows him the photo of the pod, something Chase scoffs at when he hears of it, thinking at first it is a hybrid. When he sees it and finds out it is from space and now in the Antarctic, he wants it. Dunbar tells him that in this violent and uncertain world...the specimen can easily vanish for a price. Dunbar gives him the precise location. Dunbar calls his butler to bring Mister Scorby to him. The butler shows Dunbar out while Chase tells Scorby he has an errand for him and wants him to take Mister Keeler along.

Winlett is dozing by the pod. He wakes up a bit and drinks some coffee yet falls asleep again. The pod breaks open and a frond comes out and seems to engulf or sting his arm. Winlett cries out and falls. The other two find him -- his face green and infected.

Colin in London asks Dunbar about the scientists' message of needing medical help. Colin has ordered a medical team to head toward the base but with weather bad at the moment, it is bound to take a few days. Dunbar mentions the people from UNIT should be arriving about now.

Amid heavy snow, a helicopter brings the Doctor and Sarah and leaves. Derek greets them, welcoming them to the loneliest spot in the world and that they were expecting someone much older. The Doctor says, "I'm only 749. Used to be even younger." Sarah announces herself as young Doctor's assistant. A dozen usually live here but are now miles away thus only the three are here. Inside, Sarah asks how they stand the weather. Sometimes it is ten below freezing. The Doctor isn't dressed any differently than usual but has his hat on. He hasn't come ten thousand miles to discuss the weather. He wants to see the sick man.

He does... Charles's body temperature is dropping rapidly, now at 46. His pulse rate is 18 per minute. The Doctor pulls the sheet partly off Charles to see the chest of the man...it is fully green and like a swollen lump of fungus or plant. His arms are also like this. Tomorrow might not be soon enough for a medical team.

Sarah drinks some tea to warm up and talks to Derek about the pod. A radio alarm goes off and Derek goes to answer it. The Doctor asks John where the lab is, angry that something has already happened.

John goes to Derek at the radio room. A message from Mike Wilson from the South Bend has told them the med team has turned back. They were in white out conditions and their Snow Cat fell into a crevice. The Doctor is changing form. Derek is a zoologist and can prepare a specimen slide when the Doctor needs a blood test. The Doctor asks why the pod opened. John tells him he put it under a lamp. "Mr. Stevenson, what you have done could result in the total destruction of all life on this planet..." the Doctor explains.

Derek prepares the blood test and takes some blood from Charles. He talks to Charles, telling they are trying their best and that help is on its way.

Outside, without gloves, the Doctor digs as John and Sarah watch. They ask him to tell them what he is doing. He finds another pod... the pods travel in pairs like policemen. They have to take into custody and put it in the freezer. Sarah asks who sold the freezer to him... an Eskimo? Winlett is barely recognizable. He is turning into some kind of hideous monster. The Doctor looks at the blood sample...no blood platelets but when John looks he tells the Doctor they are schizophytes -- smallest known organisms, plant bacteria. "Interesting isn't it? A human being who's blood is turning into vegetable soup?" The Doctor reflects.

They hear the sound of engines. John and Derek will go outside, thinking the medical team has arrived. Sarah asks the Doctor if they can help the man. The Doctor doesn't know. Charles is half way to becoming a Krynoid, a kind of galactic weed, he explains to Sarah. On most planets, the animals eat the vegetation. On planets where the Krynoid gets established, the plant life eats the animal life. He doesn't know the definite answer to why they are in space: the planet of origin might have an unstable surface, causing explosions and sending some matter into space. Sarah wonders what they can do about Winlett. The Doctor tells her he is thinking.

John and Derek bring in two frosty men. Sarah helps to seat them. These men were flying a private plane and got themselves lost...at least that is their story. The Doctor asks John to take a look at the patient. When the others are gone, Scorby, one of the men, and Keeler even if they didn't swallow their story -- a lie -- there is nothing they can do anyway.

The Doctor, Sarah, John, and Derek see that the process on Winlett is almost complete. The Doctor suggests amputating the arm -- it might help but he doesn't know for sure. The Doctor tells Moberley he is the only one who can operate. The Doctor tells him, "You must help yourselves." Sarah tells Derek he is not a doctor of medicine. She convinces Derek he must operate -- he is his last chance. John tells him they will help him in every way he can. He agrees. "You're a good man, Moberley," the Doctor says. They leave. Winlett, half his face almost turned into a plant vein, sits up.

The monster that is now Winlett finishes killing Derek and stalks out of the building into the snow.

Scorby takes out a rifle and empties it of bullets so that the scientists cannot use it. Keeler thinks they are just here to confirm the pod is here and report back to Chase. Scorby tells him they are here to dig a hole big enough for five bodies, kill the others, and take the pod home. Scorby tells Keeler he will do exactly as he is told or that hole will just get a little bigger.

Sarah finds Derek's body. She reports this to the Doctor and Stevenson. It is true and they find Winlett gone...it is not Charles, it is the alien, not of this world. His mind is taken over and there will be a transition period before it turns totally into a full Krynoid.

Keeler and Scorby resume their fake stances as Stevenson and Sarah come in for their jackets. Sarah asks if Keeler is okay. Stevenson takes his rifle, unaware Scorby has sabotaged it. When the trio leave, Scorby tells Keeler this is their chance to find the pod.

In London, Dunbar reports to Chase: there has been trouble at the base. A telex message about a virus infection. Chase reveals he sent his most efficient man to Antarctica to require it there instead of England. This surprises Dunbar, who doesn't like this. He wants his anonymity protected. Chase tells him he always protects his employees. Dunbar took up a career hoping to reach the top but has seen others promoted over his head. Chase gives him the large amount of money they agreed on. Chase wants only the pod, Dunbar wants money.

Winlett now almost totally gone, his face covered by the face of the monster plant, stalks the snow but finds the generator plant hut -- far from camp because of the new fuel system being tested for the first time. It is scared off when the Doctor, Stevenson, and Sarah see the hut and move toward the building.

Keeler and Scorby cannot find the pod and Keeler feels a bit upset by the idea that Scorby is going to murder everyone else. South Bend calls and Scorby pretends to be Derek. He tells South Bend not to send the medical team. When the voice calls, unsure if it is Derek and asking if it is, Scorby pulls the wires out of the radio.

At the outside of the hut, the Doctor tells the other two that the monster will try to find shelter during the interphase and the blizzard outside.

Keeler finds the remains of the opened pod. He tells Scorby it germinated. Scorby wants to find the plant.

In the hut, the Doctor reminds Stevenson that Winlett no longer exists as a human being. He's a plant or vegetable. Stevenson finds it hard to take. The things are lethal. Stevenson asks how the Doctor knows. The Doctor yells never mind that...on planets where the Krynoid gets established all animal life is extinguished. Sarah mentions Winlett's name again but the Doctor shouts, "Winlett!" They all hope that the second pod is safe and the Krynoid is frozen in the snow somewhere. The trio head back to the main base. Watching, the face of the monster with roots sticking out, readies to find the shelter it needs.

Scorby and Keeler find the body of Derek and Scorby uncovers his face. Scorby has his pistol out.

The monster tries to get into the hut. Stevenson goes to check something while the Doctor and Sarah make for the entrance.

Scorby calls the Doctor to the room with Derek's body. He runs in and tells Keeler not touch the body. Scorby shuts the door and tells the Doctor to put his hands up and to turn around. The Doctor turns around fully but Scorby tells him to face him and then to start talking. The Doctor starts rambling about Wolfgang Amadeus Mozart who had perfect pitch. The Doctor tells them Derek died. Keeler hits his arm, asking how. Finally, the Doctor and Sarah explain what happened. "You could say he's not quite himself," the Doctor says of the monster. They should lock all the doors and windows. The thing wants food and warmth.

It has found it -- in the hut.

Keeler ties up Sarah and the Doctor to chairs. When Scorby asks the Doctor more, the Doctor recites the House that Jack Built, helped by Sarah. Scorby tells him he is not a patient man. The Doctor tells him his candor does him justice. He explains the man is now an alien life form. Stevenson comes in, calling for the Doctor and Miss Smith. When he pulls the rifle and shoots at Scorby, who wouldn't put the pistol down, he finds it will not fire. Stevenson is put next to the two, in between their chairs. He asks the Doctor if they have taken the pod out...but the Doctor uses his leg to try to silence Stevenson. Keeler figures this to mean there is a second pod. Scorby points the gun at the Doctor and then at Stevenson, finally stopping his gun at Sarah...and this time he is not joking. The Doctor tells him it is in the freezer. Scorby takes Stevenson to get it. He leaves a reluctant Keeler pointing a gun at the Doctor, who tells him he is all right with them, "We won't hurt you."

In another room, Stevenson tells Scorby they have thermal containers to keep the pod cool. Scorby asks about the power. A new fuel cell system half a mile from here. He tells Scorby they checked that out already an hour ago, the creature is not there.

The Doctor puffs out his lips and seems to hum a tune this way. He and Sarah talk, making Keeler more nervous. The Doctor tries to reason with Keeler. Sarah tells Keeler it is out of his control now and reminds him of what happened to Winlett. Sarah tells him if he releases them, they can fight it together. Scorby comes back in and has Keeler tie up Stevenson.

The monster is outside again, prowling.

Keeler asks Scorby if he is going to shoot the trio in cold blood. Scorby takes Sarah outside as the Doctor yells Scorby's name. Scorby gets a stalling Sarah to take him to the hut, which he tells her he knows she was at an hour ago.

Trying to untie the Doctor, Stevenson tells the Doctor it's hopeless. The Doctor says, "Nothing's hopeless. All we have to do is think." Scorby plants a bomb to the power system, which has wires going to all the other buildings. Keeler ties Sarah up. Sarah calls what they are doing, "Murder, cold blooded murder."

The Doctor hops to a lantern hanging and with his head knocks it off the rack. He uses the glass to cut Stevenson's ropes, yelling at him to get over here. And to keep still -- he doesn't want to sever a blood vessel.

Keeler tells Scorby it is murder but he tells Keeler to watch Sarah. Keeler touches her shoulder. Sarah tells Keeler they don't have to kill them since he has the pod. Scorby tells her the bomb will blow the camp to smithereens. Keeler runs to stop it but he cannot fight Scorby, who throws him outside. Scorby tells Sarah she has ten minutes or so to wait.

The Doctor has untied himself and tells Stevenson to call South Bend and send that team after all. The Doctor goes outside to find Sarah, calling for her. The Krynoid, looking for food, enters the base and kills Stevenson as he is in the middle of making the call for help to the main base (South Bend). It chokes him.

Sarah awakens in the snow and to the sound of a Snow Cat pulling up. A man from South Bend arrives with two marines who helped get them through. The man is Dr. Chester. Sarah gets hysterical and starts yelling for the Doctor. She runs to find him. She finds him buried face down but he is alive. He opens his eyes to say good morning.

Scorby and Keeler arrive back in London at Chase's estate. The black gloved Chase greets them and asks them to open the case containing the pod. Scorby explains what happened to the infected man, warning Chase not to touch it. Scorby reports the explosion. Chase feels it is a pity, "I could have had two pods." The butler shows Dunbar in; Dunbar upset about the lengths Chase has gone to in order to get the pod. Chase mentions Dunbar has been well paid. Dunbar reports the Doctor and his assistant are still alive and meeting with Dunbar and Sir Colin in two hours time.

The Doctor carries a chair past Sir Colin and tells him that greed is the reason for the lengths people will go to for the pod -- greed, the most dangerous thing in the universe. Irritated, the Doctor tells Sarah to tell Dunbar about these fanatics. The Doctor tells Sarah to be calm. They believe the two men are stooges working for someone else, someone more crazy. The Doctor is more upset by the fact that they knew of the discovery of the pod -- it had only been reported to Sir Colin's department. Info was leaked from this bureau. Hired thieves and murderers don't work for love, the Doctor tells them. Action, the Doctor says, action is what they need. If they don't find this pod, it will be the end of everything, even Sir Colin's pension. Dunbar says he will authorize and organize everything the Doctor needs. The Doctor wants to go to the botanic institute now...

The Doctor and Sarah leave the World Ecology Bureau. Outside, a limo driver tells them this car has been sent for them to take them to the Botanic Institute.

Richard Dunbar tells Chase via phone that the Doctor and Sarah are being taken care of.

The limo stops at a hillside. The chauffeur pulls a gun and orders them out. The Doctor, getting out the back, starts talking but pulls the man's hand and arm through the open window of the back door. This gives Sarah and the Doctor time to run off after the Doctor knocks the man down. He fires at them from the ground. He gives chase to them down the hill. Sarah calls the man, distracting him toward her as she hides while the Doctor is up on a small water tower after tossing a rock to distract the man further, away from Sarah. The Doctor jumps down onto the man and punches him out.

Sarah and the Doctor search the limo. Sarah calls the Doctor to the boot of the car and he steps in a puddle. In the trunk (the boot) Sarah finds a painting by Amelia Ducat, the name of whom the Doctor mispronounces as Ducat since it is spelled that way. They take the painting to her.

The old lady Ducat explains to them it is the fritilarius meliagrus. The Doctor asks if it is the common snake's head fertility but drops that question to ask who the owner of it is. Sarah explains the driver of the car tried to kill them. Ducat smokes a cigar. She tells them it was Harrison Chase, the millionaire -- "Good Lord, he never paid me."

Arnold Keeler tells Chase the experiments on the pod are not working successfully. Keeler tries to get Chase to stop the experiments. Chase wants Keeler to inject the pod with fixed nitrogen; Dunbar told Chase if they take the proper precautions the pod will be safe to experiment on. Dunbar calls to tell Keeler to tell Chase that his chauffeur is in the hospital.

Sarah and the Doctor arrive in the limo at Chase's home. The Doctor puts on the driver's hat and coat and asks Sarah how he looks. The Doctor beeps and a guard lets the car into the grounds. They leave the car not far from the mansion. Sarah suggests the front. "Not this time," he tells her. They hide from two armed guards but then walk toward the house, brazening it out as the Doctor says. The two guards call a warning but then fire on them. The pair run across the outside of the mansion and then throughout the maze of gardens. "Act natural he says," Sarah remarks. They run into Scorby who stops them. The Doctor says, "Get our hands up." Scorby calls the guards. "That's right, grab us, we're very dangerous," the Doctor tells them. Scorby tells him he is full of good ideas.

The trio bring Sarah and the "meddling Doctor" to Chase who seems to admire the Doctor's survival. "Have you met Miss Smith, she's my best friend," the Doctor smiles to him and tips his hat. The Doctor introduces Scorby and the other two men but then gets serious, "Hand over the pod." In this house are the greatest selections of rare plants in the world. The Doctor tells him to take care, he noticed a little green fly here and there. Chase plans on having the pod flower. He will have them both executed. The Doctor tells a protesting Sarah to be reasonable, "We keep interfering." Before they die, they will see his beautiful plants. Sarah asks the Doctor what he is playing at but the Doctor grits his teeth as Scorby pushes him out. Chase shows them around his exhibits.

Chase explains the west wing was built by Sir Bosewell Chase in 1587 just before his execution. He shows them the plant lab. The Doctor puts the driver jacket over the guard's rifle and gives him the hat. The Doctor does so hate guided tours. Sarah jokes about flower power. Irregular light patterns can affect the senses of so called mindless things. "Oh yes, like Scorby here," the Doctor says. Scorby tells the Doctor to enjoy himself while he can.

The butler brings tea to Keeler who notes the pericarp has something forming on it. The pod is alive and growing. Keeler sends him to get Mr. Chase.

Chase is playing an organ for the plants. The Doctor fans himself with his hat. Scorby herds them in to see Chase playing the hymn of the plants which he composed himself. Sarah whispers to the Doctor who whispers but then tells her what he said, "I said the music's terrible!!!" Scorby tells him to shut up. Chase plays his requiem. Hargreaves the butler comes in. The Doctor tells him to go away, "Can't you see Mr. Chase's busy?" Chase stops playing and asks the butler why he is shouting since the music stopped. Hargreaves calls him to Keeler.

Chase orders the two taken away and goes to Keeler. He orders more nitrogen--another 15 grams.

Scorby is taking the Doctor and Sarah on a one way journey. As they pass a trellis, the Doctor runs around it, avoiding Scorby. Sarah grabs Scorby's arm, "Now Doctor!" The Doctor kicks the gun away from Scorby's hand and punches him and turns his head, knocking him down. Sarah gets caught in the garden gate but shuts it to slow Scorby down. The Doctor grabs Sarah into a bush. He wants her to get over the wall to warn Sir Colin. He wants another look at the pod. Scorby retrieves his gun and calls the guards. More are alerted. Sarah and the Doctor hear whistles blowing. The Doctor checks the top of the wall around the estate. The hatless Doctor has found some rope and ties it around a worried Sarah. He quiets her.

Chase is fascinated by the pod while Keeler is afraid. Sarah climbs down the wall and signals to the Doctor that she is okay. She unties herself and sneaks about the outer grounds. Inside the grounds' walls, the Doctor walks down some outside steps, tosses the rope into a shrub tree and hides from tree to tree to get nearer to the house. Sarah hears some noises in the thick trees. A sadistic guard grabs her around the mouth from behind and calls her a little girl, threatening to kill her if she makes a sound. He whistles to the guard in front of them, the one who made the sound Sarah heard. Sarah blinks as he takes her away.

The Doctor smashes through the sky light window feet first, glass following. He punches Scorby down and smashes a chair over him, getting his pistol. "What do you do for an encore, Doctor?" Chase asks him. "I win," the Doctor pushes him and grabs Sarah. They leave and somehow the door is locked on Chase. As Chase bangs on it, asking why he is surrounded by idiots, the fronds of the pod and sting Keeler's arm. Chase and Scorby rush to help him, upset. A guard, the same one that caught Sarah, opens the door to let Scorby out. The Doctor hides Sarah in an alcove outside, telling her he will return to the pod. He has a pistol. Sarah tells him he would never use it. They don't know that, he says and goes.

Keeler is already changing. Chase is fascinated; he will help Keeler here, he says but he intends to watch it happen -- the change is utterly unique.

The Doctor sneaks back into the halls of Chase mansion but Scorby with a semi automatic spots him and quietly follows.

Hargreaves comes to help Chase with Keeler, shocked at his green bulbous skin. Chase orders the butler to help, not ask questions. As guards pass pyramidal trees, Chase and the butler help Keeler to another part, a cabin.

The Doctor returns to the lab, "Nobody move." No one is there. Scorby comes in and tells the Doctor it is predictable -- the criminal returning to the scene of the crime. The Doctor in unimpressed, asking questions of Scorby about the pod bursting. The Doctor tells Scorby he is working for a madman. Scorby says he pays well and they of the same religion when it comes to money, quoting an American humorist who lived from 1881 to 1960 the Doctor recalls as Franklin Adams. "The quotes are over, Doctor. Miss Smith will never get out of this place alive and neither will you." He herds the Doctor out again, telling him not to try anything. Scorby brings the Doctor, roughly knocking him down, to the compost crusher room. "Can't we talk this over, Scorby?" The Doctor asks as Scorby beats him into the canisters. "You're pushing your luck, Scorby." Scorby shows them the machine -- they make their own compost here. Always put back in the soil what you take out. Just what Chase says. Scorby demonstrates the teeth of the crusher and tells a guard to tie the Doctor up.

Sarah ventures out of her alcove as darkness closes in. Keeler in bed in his cabin is almost fully plant. He is in restraints. Protein absorption from Keeler has begun. Keeler tries to appeal to Hargreaves but the butler thinks Chase is correct, afraid of Chase or too dumb to do any thinking of his own. Chase leaves for some equipment to monitor this experiment. Sarah overhears Chase and Hargreaves discussing Keeler as she sees them leave the cabin. Hargreaves gets an urgent call for Chase from the main gate. Amelia Ducat is there, saying Chase owes her money. She is very persistent, the guard at the gate tells him. She has mentioned lawyers. Chase is convinced to see her by Scorby. Chase tells the gate guard to have someone bring her up to the library.

Sarah sneaks into the lower room of the cabin and hears moaning of Keeler's. She climbs the stairs into the room and hears Keeler tell her not to be frightened. He tells her she should be glad, "After all it might have been you." Sarah tells him she isn't scared. Chase owns him body and soul, Keeler says. This is Winlett changed. Sarah tells him she must find the Doctor. Keeler tries to get her to release him but she can't. She must get the Doctor to help him. He begins yelling at her, telling her she is as bad as Chase and she wants him to die. Sarah hides in a closet via one door as the butler returns via another, bringing Keeler a meal.

Amelia smokes in front of the fire in the library as the hour grows late. They discuss the Venezuelan plant Ducat is painting for Lady Chandleing. In high summer, Chase's mansion is better to see. Ducat wants to set up painting here but Chase puts her off. Chase owes Ducat 750 guineas plus inflation. A round thousand pounds. The house, he tells her was mostly built during the War of the Roses, charmingly named but bloody period of history. Scorby comes in and asks if they should start the recycling. Chase wants to be there. Scorby will show her out. Chase writes her a check.

Chase goes to the compost machine room -- the compost is the secret of the lush look of the gardens. The Doctor is shocked that Chase has been feeding Keeler. Sarah is in the house again and hides behind a suit of armor as Scorby and Amelia come into the hall. Ducat is stunned by the mixtures of style of the house. This part seems to be early 16th century. A guard reports to Scorby but he takes the man aside, claiming it is a security exercise. Sarah whispering, calls Amelia over to her, explaining she and the Doctor are trapped here and she must get word to Sir Colin Thackeray of the World Ecology Bureau. Scorby returns, thinking he heard Amelia talking to someone. She bluffs that she is always talking to herself. She tells him it is old age, "It happens to all of us, you know." She asks Scorby if this is the way out, getting his suspicions away from the hall Sarah is hiding in.

Chase has the Doctor tied up inside the compost machine, ready to be turned into compost. For once, the Doctor can't think of anything to say as he is about to be bodily ground by the device.

Night: Amelia meets a car outside the grounds of Chase's estate. She gets inside and in it is Sir Colin. "You're quite right, Sir Colin..." she explains what is happening. Dunbar is there as well in the car with them. Colin will alert the Doctor's friends at UNIT... this is too big for them to handle. Dunbar will get in to stop this -- he admits he made a terrible mistake. He will go in and get the two out, making amends. If he is not back in half an hour, he tells Sir Colin to return to London and call UNIT.

The butler returns with more food for Keeler but finds a mass plant man, thriving, Keeler's face completely covered by plant and with arms of fronds. Hargreaves throws the tray and runs out. Keeler, almost a full Krynoid breaks free now.

Sarah comes to the Compost Room and finding the Doctor tries to climb in to get him out as the machine is about to devour him. He yells at her to press the button. She presses one but that speeds it up! "Not that button, the other one!" She turns it off and climbs in to untie the Doctor. "Oh Sarah, it would have been such a waste."

Scorby and his two men arrive and fire at it. This distracts it from Sarah and the Doctor, who run. Scorby and his two men follow. They run to the cabin's lower part and the Doctor orders them to block the door, hissing at them to move the couch quietly. Scorby asks how the Doctor does it -- he should be compost by now. Sarah tells Scorby that thing used to be Keeler. Chase beeps on Scorby's radio. Chase does not want the thing harmed. Scorby tells him it is 8 foot high and already killed Dunbar. Chase tells him people are replaceable, the Krynoid is unique. Scorby tells him he cannot get through to him but the Doctor takes the radio and tries to get through to Chase but cannot. Chase won't listen that the Krynoid is carnivorous. Outside the monster mass makes strange sounds. Scorby asks how big the thing will get. The Doctor thinks about the size of St. Paul's cathedral and after that it will multiply itself a thousand fold until it takes over the entire planet. A tentacle smashes through one of the other wall's windows. Scorby shoots at it and goes to the steps. Sarah hacks at it with an axe but is thrown. The Doctor uses the sword. The tentacle moves out. The Doctor yells at it, "You don't scare us, Keeler." He looks at Scorby, "Do you think he believed us?"

The Krynoid voice tells them the human was Keeler. It asks the Doctor to come out and join them. Sarah reasons it is afraid it will find a way to destroy it. Keeler is now one of them. It seems to sense its knowledge of alien species. It tells the others if they give the Doctor to them, their lives would be spared. Scorby argues with Sarah about giving the Doctor to the creature. The Doctor has heard what the thing is offering them before. The thing tells them they have to daybreak to deliver the Doctor. By daybreak the Krynoid will be large enough to crush the cabin to rubble. The Doctor asks Scorby, after yelling at him, if he can make a firebomb of some kind. Scorby can make a Molotov cocktail.

Amelia smokes in Sir Colin's office while they wait for word from UNIT. Amelia wonders if they should have gone back to the grounds. Sir Colin tells them it is too dangerous. She tells him about the armed men on the grounds but that she wasn't afraid. She was in the armed services. She likes a bit of excitement. She was a sergeant in the ATS and something about Folkston and manning a cannon or something. The Brigadier is in Geneva. Amelia tells Sir Colin to invent a code word: operation nuthouse. They will send a Major Beresford. Amelia insults civil servants but Sir Colin tells her he is a civil servant. She replies then he knows exactly what she means. As she leaves, she returns again and tells him to consider her available for any future assignments, hoping that they will get help to the Doctor and dear little girl.

Chase prepares to take the first pictures of an alien organism. Hargreaves tells him to be careful. Chase tells him he has nothing to fear from it.

It is dawn it seems. Scorby is ready. The Doctor will contact Sir Colin and tell him that his world is about to fall apart. He wants Scorby and Sarah to run to the main house and secure it as a link while he goes to warn Sir Colin. Scorby tells the Doctor that for the moment he can rely on him. The two men clear the door but the Doctor hisses to do it quietly. The Doctor suggests Scorby lob the bomb from the main window.

Chase goes outside to see the Krynoid has risen to the heights of the house and above.

Scorby tosses the firebomb. The Doctor runs out as it chases him. Scorby and the men run out with Sarah. The Doctor gets to the limo and drives off, the giant monster mass following him. Scorby and Sarah find Hargreaves in the greenhouse. The butler tells the pair that Chase is outside taking photographs. Scorby has posted lookouts. Scorby orders the butler to help board up the doors and windows. Scorby mocks the Doctor getting out of trouble. Sarah tells Scorby that the Doctor has risked his life for others unlike him. He threatens Sarah that if she pushes her luck by insulting him, he will start again where he was before. Sarah tells him he is not complete unless he has a gun in his hand. She calls him as mad as Chase.

Chase is outside taking pictures of the giant beast. It watches him and starts to move to him to kill him. Chase calls it Keeler as the shadow of it block him. He wants to help it, he says up to it.

Major Beresford is with Sir Colin now. He will not mount a raid on someone's private estate or property. The Doctor pulls up in the limo, parks in a no parking zone, and runs into the offices. As the male secretary tries to stop the Doctor from entering the office where Sir Colin is in private conference, the Doctor shoves him, "Out! Out! OUT!" The Doctor calls Beresford's reluctance to raid Chase's private property, "Waffle! Waffle! Waffle!" When Sir Colin's phone rings, the Doctor picks it up and says, "He's busy!" He asks where the Brigadier is. He is in Geneva. The Doctor tells them a revolution is going on. All the vegetation is about to turn hostile -- somehow the Krynoid can channel its powers to other plants. Colin jokes about aggressive rhubarb; Beresford laughs about homicidal gooseberries. He shows Colin a report he snatched from the secretary: 55 year old gardener found strangled to death in rose arbour, every cultural worker found strangled in field. The Doctor tears it from Colin's hands and gives it to the Major. He reads: 35 year old woman strangled in garden maze. The Doctor yells at him to read another bit: all these deaths happened within a mile of Chase's estate.

Sarah gets a call from the Doctor. The Major is getting a laser gun team together to stop the Krynoid. The vines on the roof of the estate snap the phone wires just as Sarah tells the Doctor she and Scorby are great friends...or uneasy allies. The Doctor has told her he is coming back with a Sergeant Henderson. Just as the phone goes dead, the plants and trees smash through the windows near Sarah.

The monster moves from the house to Chase, who is on his back on the lawn in a kind of trance like euphoric state. He says the plants must win, a new silent and beautiful world.

Scorby comes in with planks to Sarah who tells him about the vines getting thicker. He agrees with her. Scorby wonders if it was the ghost of Sir Bosewell Chase, his ghost is supposed to haunt this place. They argue but the vines start coming back in. They duck but Sarah tells him the Doctor is on his way back. The butler comes in and tells them the guards have all left. Scorby calls them like a bunch of women. Hargreaves heard screams but he didn't go out. Sarah wants to go take a look. Scorby tells her they cannot, since that thing is out there. Sarah tells him someone is obviously in trouble. He won't go. "What was that you just said about women!" Sarah stalks out. Scorby follows her.

In the outer garden, they find a guard strangled by the vines. "Doctor, where are you?" Sarah asks. Chase appears and tells them he has taken fascinating photographs. Chase feels the world is the plants' world... we humans are merely parasites. Scorby tells Sarah that Chase is out of his head, he is really gone. Sarah says, "He must have been gone for years if you ask me."

Chase is in his greenhouse on his table, playing his organ music, talking to his beautiful friends. A new era dawns upon the Earth. Plants will be restored to their position of dominance. Hargreaves blocks the door but Scorby moves him out of the way. He and Sarah go in to try to reason with Chase. Scorby shuts off the organ music and goes out to Chase, asking him to listen. Chase talks of harmony of root, stem, leaf, flower. Sarah and Hargreaves are with Scorby. Scorby wants to know what to do. Chase tells them it is "our" turn. In his mind, Chase is one of the plants -- he hates animals -- it is only a matter of time before they all die. Hargreaves tells Scorby that Chase is ill and to leave him alone. Sarah spots the plants moving all around the centre of the dias, trapping the trio on it with a happy Chase, who is not endangered at all.

Sergeant Henderson opens the gates for the limo and the Doctor drives in. Henderson gets in and they drive toward the main house.

The vines have covered the dias and are strangling Scorby, Sarah, and Hargreaves. Chase tells Scorby not to resist it. He must die... all plant eaters must die.

Beresford and his men see the towering Krynoid over the roof of the castle. He orders his men to fire the laser gun twice. The monster giant moves at the UNIT men. The Doctor leads the trio to another door, running behind the giant as it moves off. The Doctor pushes them all inside. Chase hears two more laser shots. Beresford orders it hit in the chest and some more shots have no effect. It moves toward the UNIT men and the Major.

The Doctor and the others return to the lab. The Doctor tells them they have to find Chase and get a hold of him before he gets another attack of megalomania, "The Krynoid on the outside, a madman lurking inside... not a happy situation." Sarah asks if Chase is counting on the Krynoid sparing him. Henderson says that Major Beresford did his best even if it was like using a pea shooter. The Doctor shushes him and tells him he thinks they have been wrong about Chase up to now. Henderson starts to say something more but the Doctor snaps, "Will you just shut up a minute please!" Chase is either infected or possessed.

The UNIT men are still running.

The Doctor instructs Scorby and Henderson to look for Chase one way as he and Sarah go another. Chase sneaks out of an alcove in the corridor and goes back to the lab. He finds the defoliant, "Filth." He smashes the radio interior. In a hall, the Doctor opens a door to find vegetation all over it. He closes it. Henderson comes to he and Sarah and they go to remeet Scorby.

Beresford tells Sir Colin at the gate what is happening. The Major is going to try to get through with a couple of men. They see the giant mass of the Krynoid sitting on top the house now, massive tentacles growing larger and thicker. One smashes through the windows and menaces Henderson in the lab but withdraws. Scorby calls it a siege. Part of the ceiling comes down and pieces hit the Doctor as the tentacles lash the roof. Henderson goes to get more timber to block the window. "Yes, you go and do that," the Doctor says.

Chase listens and hits Henderson in the back of the head with a wrench and drags him out of the area he is in.

The Krynoid makes a large hole in the roof and ceiling above.

Scorby tells the Doctor he still thinks they should make a run for it. The Doctor tells him that everything that grows in the ground is against them, they wouldn't get far. Sarah tells Scorby not to be so negative and that Major Beresford will think of something. Scorby says, "Oh yeah!" The laser gun was useless. Scorby never relied on anyone--he always got himself out of trouble. Africa, the Middle East, being a mercenary: "I'm a survivor, right!" Watching out the window, the Doctor wasn't fully listening, "Scorby bullets and bombs aren't the answer to everything." The building shakes and more rubble comes down. Scorby continues to panic. Sarah tells him to just shut up. Scorby tells them their precious Beresford will just pick up and run. The Doctor tells him, "Not anymore than you would, Scorby."

Chase has tied up Henderson and placed the unconscious man in the compost machine. The body heads at the teeth of the device as Chase callously watches.

The Doctor thinks he can fix the radio. Scorby is in a kind of negative shock, mumbling to himself about their deaths which he thinks are to be soon. The Doctor tells him to stop feeling sorry for himself -- it can become a habit. The room shakes again and some more rubble comes down. Despite Sarah's screams and the Doctor's warnings that he will never make it, Scorby removes a filing cabinet from the door and flees outside. Sarah almost reached him to stop him.

Outside, Scorby runs through a wild mesh of plants, vines, trees, and shrubs. He makes it out of the thick of them but splashes into a small lake or pond full of vines and weeds. He seems to be making some headway but is stopped. A small wall of plant material rises up to become a larger wall. It covers him and drowns him into the water. The weeds cover him in the river.

Beresford and some men arrive back at the area. Inside, Sarah hears the plants getting into the boiler and humidity system -- they could blow it up or create a scalding shower. The Doctor calls for Sergeant Henderson. He sends Sarah to find him. He needs the correct wavelength to make the radio work. Carefully, Sarah calls for the Sergeant, whispering. She goes into the compost room where Chase is hiding in a corner, "The Sergeant's no longer with us. He's in the garden. He's part of the garden. We're helping the plants grow the Sergeant and I in different ways, of course." Chase rambles on about the Krynoid thanking him and how the foul species of Sarah and her kind--parasites, who depend on them -- the plants for the air they breath and the food they eat -- will soon become extinct, "We have only one use for you." Chase, a mad look on his face, rushes at Sarah.

The tentacles start to lash at the side of the house now.

Beresford calls other men, using the code name Scorpio secton. He reaches the Doctor instead. They have 15 minutes before the Krynoid reaches the primary point of germination. Sir Colin gets on and asks what that means. At that time, the Krynoid will eject hundreds of spores -- embryo pods -- by the hundreds and doom not only the Western Hemisphere but the whole planet. The Doctor tells them a low level aircraft attack with high explosives. It is the only chance for the planet.

The Doctor gives the lab one last look and tosses a piece of rubble.

Beresford tells Sir Colin the planes are on their way and in 3 minutes will be here. Sir Colin wonders if there is any way to get them out.

Chase has tied up Sarah as he did to Henderson before her. He starts the machine and Sarah begins to move inward toward the teeth. She begins to wake up from her unconscious state. The Doctor rushes in, tosses Chase down, and stops the machine. He jumps in and unties Sarah's feet and legs and puts her out of the machine. Before he can untie Sarah's hands and arms, which are behind her, or get out of the machine himself, Chase restarts the machine. The Doctor falls into the case as it moves at the teeth again. As the Doctor tries to get out, Chase throws himself at the Doctor and both end up fighting inside the cart as it moves toward the teeth-grinder. The Doctor gets up from the fallen fight and climbs over the edge, Chase pulling him toward the cart floor again. Sarah cannot reach the button with her elbows. The Doctor tries to pull Chase out of the cart but Chase continues to try to pull him back into it. Finally Chase's hands slip off the Doctor's and he screams. The Doctor looks away. He unties Sarah's hands, telling her he tried to save him but Chase kept trying to pull him in. Sarah cries, "Couldn't reach." He herds her out.

Sir Colin and the Major see the sighting run of the planes. The Major calls them. He looks with binoculars at the house, now almost completely covered by the Krynoid.

The Doctor and Sarah rush to a door but it when they open it the exit is covered by a wall of plants. They slam it shut. Sarah leans on the door, "Where do we go? We've got the Krynoid outside, steam inside, and bombs overhead!" Hearing steam gives the Doctor an idea. He slowly and painstakingly removes a pipe from the steam boiler and tells her to stand by the door. He shoots a jet of steam at the mass of plants, allowing for he and Sarah to get outside and away. Still, they have to fight through a mass of vines, trees, leaves, and finally they jump behind a fallen log.

The planes fire rockets and this blasts the house and the Krynoid, blowing them both up and incinerating them.

In Sir Colin's office, Colin asks the Doctor if they have seen the last of the Krynoid. The Doctor explains that he is quite naturally President of the Intergalactic Flora Society and that the society finds it difficult to study the Krynoid, "Their researchers tend to disappear." Sarah says, "A case of one veg and no meat." As Big Ben rings, the Royal Horticultural Society would like the Doctor to address one of their affairs. It is on the 15th but the Doctor tells Sir Colin he cannot do that -- he's solidly booked for the next two centuries. Sir Colin laughs, "Doctor, I never know when you're being serious." Sarah stands up, "I know just how you feel, Sir Colin." The Doctor asks if they've ever heard of Cassiopeia. "Animal, vegetable, or mineral?" Sarah asks. It is a terrific planet for a holiday. They need a break. The Doctor asks Sir Colin for a little excursion. He would be delighted but his wife is expecting him home for tea.