DOCTOR WHO IN DETAIL

In an underground tunnel a team are digging when the tunnel starts to collapse. Most of the team is okay, but Captain Revere is caught by falling debris. Brazen calls for a block and tackle to lift off the debris, but when he turns back Revere's body has gone. Brazen orders the remaining team to mention the incident to no-one.

In the TARDIS Turlough is concerned about the Doctor, who is acting stranger than usual. Turlough and Tegan can hear the Doctor making a lot of noise trying to tidy up the TARDIS, which includes taking the hat-stand from the console room. Turlough check the console and finds something is happening to the controls, and on a screen a Boundary Error: Time parameters exceeded error is showing. The TARDIS has drifted too far into the future, and the Doctor puts it into 'hover' mode in the Veruna system.

On the view-screen Tegan can see the planet Frontios where the colony of humans, escaping from the 'doomed' planet Earth, is established. Tegan wants to visit them, but the Doctor is reluctant to, using the 'Laws of Time' as an excuse. As the Doctor is about to leave the TARDIS caught in a gravitational pull and is dragged towards the planet along with a number of meteorites.

In the colony Science Office Range is asking for an enquiry into Revere's death, but Brazen says there is no need for one, and that Revere's orders that the Research Centre be shut down in the event of his death still stands. He also shuts down the communications system, and says that the colony is now under military jurisdiction.

The TARDIS materialises on the planet just as the meteorite storm passes. Immediately the Doctor sees an injured woman and ruses to help. More injured colonists are taken to a small hospital, and the Doctor and Turlough help the woman there, where the Doctor takes charge of treating the wounded. The medical facilities are not up to much; the only lighting from greed phosphor lamps that are dangerous. The Doctor sends Turlough and Tegan back to the TARDIS for better lighting and medical supplies. In the TARDIS the interior door seems to be locked.

Brazen informs the Plantagenet of the Doctor, Turlough and Tegan's arrival. The colony is at war, but they are not sure who. Brazen surmises that the Doctor is the start of an invasion.

Without access to the lighting from the TARDIS Turlough learns from Norna about equipment in the Research Room that may help. Turlough and Tegan go with her to fetch the equipment back, even though that area is now out of bounds. As Norna leads them into the original colony ship that crashed the Doctor learns more from Range about the colony, and about how Revere thought the attacks were someone reclaiming their territory from the humans. Range tells the Doctor that the colony had 10 years to get started, and that the first missile landed around 30 years ago.

In the crashed colony ship the door to the Research Room has been sealed, but Norna leads Turlough and Tegan over the hull of the ship and through a hatch to get inside where they find a battery that they need to provide lighting to the hospital. There are guards on the hull, and to avoid them Turlough manages to rig up a pulley system to lower the battery down. They are caught by the Warnsman, but Turlough swings the battery, rendering him unconscious.

In the hospital the Doctor is confronted by the Plantagenet, who does not believe the Doctor is there to help, and thinks he is part of the invasion attempt, especially as his companions have been seen entering the hull of the colony ship. The Doctor offers to show the Plantagenet his ship, but when they go outside a bombardment has started. Everyone runs for cover, and when it has passed the Doctor, for once, is eager to leave. He and his companions make their way back to the TARDIS, only to find it seems to have bee destroyed in the bombardment, the only remaining part being the hat-stand.

The Doctor is confronted by the Plantagenet, and is about to be shot when Norna stands in the way When the starts asking about the rocks under the colony that Revere had been interested in Turlough tells the Doctor about the Research Room, and the Doctor asks to see it. When the Plantagenet refuses Turlough brandishes the TARDIS hat-stand like a weapon, and the Plantagenet orders the Research Room to be reopened. In the room the Plantagenet tries to attack Turlough, but Turlough points the hat-stand at him, and he collapses and is taken to the hospital.

The Plantagenet has a weak heart, and his collapse was the effect of a blow during the bombardment. At the hospital the Doctor uses the battery, that Tegan had been helping Range plug into the lighting, to shock the Plantagenet's heart back into life. After resuscitating the Plantagenet he is more trusting of the Doctor, and tells him about the troubles the colony had been having to get established.

In the Research Room Turlough learns more abut the colony from Norna. She tells him that Revere, many years ago, said the earth was hungry, and ordered all drilling to stop, and forbade anyone from going underground. But in the room there is a block and tackle for moving the metal floor plates, which had been installed after the order had been given. Turlough removes one of the plates to find a tunnel underneath the room. Turlough is spooked: the rock formations underneath the colony remind him of some he has seen before. Norna wants to explore further, and as they do so they fail to notice the giant slug-like creatures hidden disguised against the walls.

The Doctor and Range go back to the Research Room and find it empty. When Range sees the entrance to the tunnel he tells the Doctor that he suspected that Revere thought there was something under the ground that should not be disturbed, and that Norna and Turlough could be in danger. They both go into the tunnels to look for Turlough.

Back at the hospital, after learning about information being spread by Range Brazen goes hunting for him, leaving Tegan and an orderly behind. Tegan checks on the Plantagenet who is in pain, being sucked into the ground. Escaping from the hospital Tegan makes her way to the Research Room and into the tunnels.

In the tunnels the Doctor and Range come across Turlough who is petrified, screaming about Tractators. The Doctor goes to look for Norna . Tegan, finding Turlough and Range, goes to look for the Doctor. Norna has been captured by the Tractators, and as the Doctor tries to warn Tegan he is captured also. When Tegan smashes one of the Phosphor lamps on the ground the Tractators scatter, freeing the Doctor and Norna. Tegan and Norna return to Turlough and Range. The Doctor tries to buy them more time by distracting the Tractators, and Tegan goes back for him.

Range, Norna get Turlough back to the Research Room where they are caught by Brazen and several troops and taken to the State Room where Range is questioned by the Deputy about medical records about 'deaths unaccountable.' Turlough, still in shock, starts talking about Tractators that had been on his planet. Brazen demands to know more about them from Turlough. Turlough explains that some of the victims of the Tractators, including Revere, may still be alive, as the Tractators need living minds. Brazen organises a small squad to go down into the tunnels for a sortie.

In the Tractators' lair the leader, the Gravis, talks to the Plantagenet about their need for human minds. They have a machine that excavates the tunnels, but it needs a human mind to drive it. In the tunnels the Doctor and Tegan are led to the Tractators' laid by the excavating machine - which is being controlled by Captain Revere. The Gravis has heard of the Doctor - at least by reputation - and shows the Doctor the centre of their operations. Tegan lets slip about the TARDIS, and the Doctor quickly covers it up, but the Gravis sees the TARDIS as a way to get off Frontios after being there for 500 years. The Gravis tells the Doctor, and the Plantagenet, that the crash was no accident, and neither were the bombardments. They were all down to the Tractators' gravity beams.

When Brazen distracts the Gravis the Doctor is able to stun it using power from the excavating machine, and free the Plantagenet. Brazen is caught by the machine and tells the Doctor to get himself and everyone else away. Away from the Tractators the Doctor has time to think, and realises the Tractators are trying, through the tunnels, to create a gravity motor which would allow them to pilot Frontios anywhere. As more Tractators come they move on. Tegan is separated, and finds panels of the TARDIS behind some of the tunnels. She calls out to the Doctor, but is confronted by Tractators. She finds one of the TARDIS doors, and finds herself in the console room, along with the Doctor, Turlough and the Plantagenet.

Turlough has told the Doctor the Tractators don't really have a lot of power - they draw power from the Gravis. The Doctor has a plan to isolate the Gravis by drawing him into the console room. The Doctor hints at controls that will draw the TARDIS back together, and the Gravis activates them. With its power added the TARDIS is drawn back together. Once the outer plasmic shell is restored it is isolated from the other Tractators.

Leaving Turlough and Tegan on Frontios the Doctor takes the Gravis to the uninhabited planet of Kolkokron. He returns for Turlough and Tegan, but leaves the colony with the hat-stand as a parting gift.