On a field on Earth, the Doctor appears after a few tries. It takes Harry four times to appear. The Doctor asks, "Are you coming or going or going or coming?" Harry tells him he feels like a Morse message, slightly scrambled. The Doctor tells him they should set about their work but Harry asks about Sarah. They hear her yell as she falls on her backside. The Doctor sends Harry to help her, finding the transmat circle of devices not only oscillating but also elipsing. Harry helps her up, calling her old thing. Sarah tells him, "Harry, I am not a thing." Only her dignity is hurt. She races off to the Doctor and pulls her grey wool hat over eyes, "Ummm Ummm." The Doctor doesn't look up and says hello, "You're looking well." The Doctor tells them to look around, it is a glorious day and no one has set foot on the Earth for thousands of years. Sarah translates that as, "In other words, you're busy and you're telling us to push off." The Doctor tells her he would have put it more eloquently but YES. Harry thinks they should do a reccie of the area. The Doctor points out where Trafalgar Square should be and Piccadilly. Sarah doubts both, especially since there is not a pigeon in sight. Harry and Sarah have moved off from the Doctor.

Sarah finds the barren landscape of fields and rocks with its constant wind and unearthly quiet, "Creepy, not like Earth at all." She hears a sound but Harry doesn't. Something move above them on the cliffside. Sarah thought she saw it. Harry protests that no one is here. Sarah tells him they don't know that, "There could be anything here... mutations... creatures."

Erak, a spacesuited man, leaves Zake, another spacesuited man to go get help. Zake is pointing a laser rifle at the Doctor, from a hidden vantage point on a hillside. Erak runs to Krans, another of their crew.

Harry falls down a hole that was covered with broken branches -- a deliberate trap. Sarah goes off to fetch the Doctor. Harry just says, "I'll wait here."

A strange box shaped machine comes up behind Zake and chases him. He throws his gun down and runs but falls off a cliffside and breaks his neck. The Doctor hears a scream, thinking it is Harry, and goes to find him. He finds the dead Zake instead. Erak and Krans find the Doctor standing over the dead man and they shoot the Doctor with one of their guns. The Doctor falls.

"Doctor!" Sarah runs to the transmat circle and finds the Doctor's sonic screwdriver but no Doctor.

Above him, Harry hears a noise. Large rocks are thrown down at him as he called up. He avoids the rocks and finds a way under some brush from trees.

Sarah calls out, "Doctor!!!"

Erak and Krans move the Doctor while another man, Roth, dressed in the same crew outfits they are in, watches.

Sarah returns to the hole Harry fell in and finds him gone.

The two men cut the ties on the Doctor's feet but leave his hands tied. The Doctor is up now and awake. He tries to convince them of the truth about his being here.

Sarah drags a tree branch to the pit to climb down and sees something moving, quickly, a glimpse only. She doesn't realize that somewhere else, Harry is climbing up the other side of some huge rocks. When he gets up between two rock walls, he finds a hillside of more rocks and grass to climb. Roth grabs Sarah from behind, covering her mouth. They hide as that strange machine on metal legs arrives. After it goes, they talk. Roth seems strange and bothered. He was the one who covered the hole but only to trap the machine. The machine serves him in the rocks... the thing in the rocks...the alien. Roth will not get caught again. Sarah finds burn marks on Roth's arm -- the alien tortured him and killed two others -- Heath and Spear.

Vural, the leader of these crewmen, comes to the Doctor and the other two men as the Doctor continues to explain that Zake was dead when he got there. The three men tell him that Space Station Nerva is just a myth like the lost colony legend of Atlantis which the Doctor tells them was a legendary city. The Doctor asks them if they are from their own lost colony. They are from Gal-Sec 7. Nerva knew there might be colonies surviving and will be happy to know they are not the only humans left, "You are human, aren't you?" The Doctor adds, "Oh, no offence." He looks at a small nub on the neck of Vural's spacesuit and deduces that it is not human technology but alien. Something alien is watching the Doctor's face get up close to the nub. Something with three fingers (but later it seems to have five or four). One of the fingers activates the mechanical robot thing.

Vural kicks the Doctor away from him, calling the Doctor a freak. Erak and Krans wonder if the Doctor is telling the truth. Nerva, if it did exist, must have been burnt up in the solar flares, Vural suggests. But the Doctor's story is so unbelievable it just might be true...why not make up something more believeable, less of a crazy story?

Roth shows Sarah the area he saw the Doctor taken to. He won't go on because the leader, Vural, he saw taken by the alien. Then the alien, he tells Sarah, let Vural go. "Vural's been hooked."

The Doctor continues to try to tell the truth -- about the humans being on Nerva for 10,000 years. The men ask about him. He tells them he is a time travelling expert. A kind of clock expert, Vural asks what kind of expert. The Doctor says, "Yes, horologist, actually and chronometrist. I just love clocks -- atomic clocks, quartz clocks, grandfather clocks...cuckoo clocks," he says as they begin to yell at his ranting. The men tell their story: they received a distress signal from here. One of their Gal Sec Freighters went missing. As soon as their rescue ship landed, it was vaporized. There were nine others and the rest vanished. Erak figures it has something to do with the circle of the Doctor's. The Doctor suggests a solution -- pop up to Nerva with him and they can call their home. Vural tells him if he is one of the old people from Nerva, while they were sleeping, his people, the Earth people put bases all across the galaxy...built an Empire, "I'll have none of this Mother Earth rubbish!"

Roth sees this and distracts them, running fast. Sarah, as the men follow Roth, frees the Doctor, who asks her, "Who's your fast friend?"

Vural asks why Roth ran from them. The men return to find the Doctor gone. The Doctor and Sarah follow Roth but the Doctor asks about his sonic screwdriver, not worrying about the pit, "I feel absolutely lost without it." Sarah tells him to never mind about it, she has picked it up and gives it to him. "What would I do without you," he smiles at her.

The Doctor and Sarah catch up to Roth. The Doctor finds the burn marks of the machine and realizes the machine is run on Tellurium drive. Tellurium is not found in this galaxy. The Doctor notes Roth is half demented with shock. Sarah explains. The Doctor comments on Harry's stupidity, "Typical of Harry, how anyone in his right mind could fall down a ravine..." Sarah explains it was covered. The Doctor goes to take a look despite her warnings and he too falls down it and seems unconscious. After screaming, Sarah and Roth lean over to see if he is all right but the machine comes up behind them!

Harry climbs up the hill of rocks and sees a silver sphere.

Water dripping on the Doctor's face, from the rockside, wakes him up.

Sarah calls it Lynx again telling it she encountered it in the 13th century, calling it the same ugly identical... he tells her he is Field Major Styre of the Sontaran G-3 Military Survey. It examines her face and records assessment -- she has no military justification. Roth, off the wires, runs but Styre shoots him dead. Sarah screams and it asks her why she made that disagreeable sound. He tells her he is a warrior but she yells at him, "Murderer! Murderer!" Styre tells her that the moron was of no further use. "You as a female are far more interesting."

In the pit, the Doctor finds a tree branch to get out. Something is above, moving about. He climbs up to it--it is the three men again, "Oh, it's you again. Can't say I'm delighted -- it's no use pretending."

Among the rock maze, Harry finds another space suited man manacled with his hands up, deprived of water. Harry finds a rag and wets it.

The three men help the Doctor up and tell him, "No tricks." The Doctor yells, "Behind you!" They repeat, no tricks but the machine whips out three metal wires to wrap around them and capture them. Their guns are no use on it.

Harry tells the chap he is helping that he will have to get more help to free him. The Sontaran left this man here to die.

The Doctor smells something in the pit, "Not the control line," thinking it was once an old sewer line. He can go through it.

The Sontaran has Sarah tied up sitting against a rock and knows Sarah wasn't on the Gal Sec ship. Sarah has a red circle put on her head by the monster. His reports can never be wrong, Sarah yells at him. She, to him, is a mistake and those must be eliminated. He presses a button on a device. Harry has a stick to beat him but hides as the Sontaran leaves Sarah and goes off. Sarah calls to a calling Harry, who finds her, "Hang on old thing. Don't you worry, old thing." Harry is stopped by a forcefield around her. Harry will knock his head off and grab his "bloody" keys. He goes.

G3 military assessment survey Styre reports to a Marshall via a scanner set in the rocks. He has lured humans here and found they depend on organic chemical intake but inconsistencies have arisen. The Marshall will have one final report within the hour.

Experiment 7: the female and resistance to fear goes on. Sarah sees a snake on her arm and rocks falling at her from above. She screams, then looks down and sees a living glop of mud devouring her feet. She screams again but the Doctor is there and using the sonic screwdriver to break the forcefield device which is hidden in the rocks. He gets to her and tells her what she is seeing is not real. It is too late: Sarah seems to pass out. The Doctor feels her face, "Oh Sarah." Styre returns and the Doctor attacks him, "You unspeakable abomination!" Styre hits him down, telling him he merely resurrected the things in Sarah's pathetic little mind. The Doctor gets up, fakes that Harry should fire and turns the Sontaran around. He runs but doesn't get far. Styre shoots him down, calling him, "Worm."

The machine brings the three other men to Styre, not far from his spaceship. Vural tells Styre he helped him, he was to be freed. Styre tells him he will not let him go -- a traitor to his own kind. The other two men realize Vural lied to them when he told them he was lost on that first night.

Harry checks both Sarah and the Doctor, "Not both of them." He checks the man on the rocks that was deprived of water and finds him dead, "Murdering swine." Styre returns to the dead man and reports on this experiment Five -- human resistance to fluid deprivation. The man was kept without water for 9 days and 7 hours. Harry moves to hit the monster with a stick but the Doctor grabs him from behind and covers his mouth. Styre reports that humans are also susceptible to immersion in water as Experiment 4 showed. H2O death will occur in 3 minutes if a human is submerged.

The Doctor tells Harry that the synestic lock mechanism from Nerva's rocketship that he put in his pocket, saved him -- the ray hit that. "Never throw anything away, Harry." The Doctor searches his pockets for his 500 year diary, wondering where it is. He knows he made some notes about the Sontarans in it, "It's a mistake to clutter one's pockets, Harry." "Yes, Doctor." Sontarans never do anything without a military reason.

One of the men calls Styre a lump of filth as he conducts Experiment 8 -- resistance of body tissue to excessive pressures. A gravity bar held by Erak and Krans is over Vural -- all tied by ropes to them all. It can be made to weigh more. Styre makes it weight 200 pounds--it will crush Vural soon.

The Doctor goes to the Sontaran ship but the machine comes at him. He says, "Hello," and tells the thing not to be afraid of him, "I won't hurt you. Everything's going to be all right, I won't hurt you." He lied as he points the sonic screwdriver at it and it falls on its legs and crashes to the ground.

The gravity bar is up to 500 pounds now. Styre hears a call from the Marshall and raises the bar upward, delaying the experiment. The men see a knife he left. The Marshall tells Styre the invasion fleet is held up. The Strategic Grand Council, the military leadership group, has given Styre orders for his reports and experiments. The invasion cannot go on without these.

Styre returns to the men.

Harry gets Sarah up to the Doctor, who is thinking, staring off. "Ahh, Sarah, feeling better? No, don't tell me---there's no time." He goes on to tell that the Sontarans must have some strategic advantage over their endless war against the Rutans in order to come this far to invade the Earth. The Doctor finds only one way, "I'm going to take him on in single combat. Sontarans never turn down a chance to kill somebody." Harry and Sarah protest but the Doctor tells them the Sontaran is pretty unwieldy for all his strength and not used to Earth's gravity. As he does this, the Doctor wants Harry to take the sonic screwdriver, go into the ship, and do something. He will tell him what.

The Doctor appears over the rocks as Styre continues the 8th experiment. The Doctor mocks him, telling him that those puny creatures he tortures now are not the real human warriors--he is. The ones he has been testing are the slave castes, the Doctor claims -- "Could those puny creatures conquer half a galaxy?" He is the warrior class of Earth and he dares Styre to fight him, challenging him to single combat, unless Styre is afraid. He also mocks Styre's use of a gun. Styre takes the bait and his machete and comes at the Doctor. The Doctor has a stick and fights him.

Sarah and Harry free the three men, lifting the gravity bar off Vural. Harry goes over rocks to the spaceship and opens the door with the sonic screwdriver. He goes in and targets some odd contraption.

As he does this, the Doctor and Styre battle. The Doctor falls down. Styre is weakened but promises to finish the Doctor later. He walks back to his ship but the Doctor jumps on him from a higher up rockcliff. Styre falls and drops his machete. Yet he manages to stand and knocks the Doctor down yet again. With the Doctor down, the Sontaran comes at him with the machete but Vural interferes and is hit down in his place, killed. The Doctor tackles Styre again, holding onto him until he can see Harry leaving the spaceship with the contraption. "You're weakening, Styre!" Styre yells, "Am I!?!?" He hits the Doctor down again but has lost his machete again. Styre flips the Doctor onto his back, "I shall kill you all now!" He goes into his ship. Sarah and Harry run to the Doctor, Sarah telling him that Vural is dead, "He saved your life." "I know," the Doctor claims, "Everybody out -- fast as you can!" The trio run as Styre's ship smokes. He comes out of it and falls, his face melting inward like a balloon. His body follows. He is dead, a deflated balloon. The ship blows up.

The Doctor tells Harry he did it. Harry asks, "What did I do?" The device, which the Doctor hoped was the right one, was a turide endiode bypass transformer. Sontarans feed on energy but by altering things a bit -- and removing this, the energy fed on the Sontaran. The Doctor takes care of the invasion fleet ready to pounce by going to the TV screen and telling the Marshall this is his waterloo. The intelligence mission is destroyed and the invasion plans are in their hands. The Marshall yells that they will invade but the Doctor smiles, "What? Without Styre's report?" "Next time, human."