Just are the Doctor gains a tentative trust from the humans, a Silurian battle cruiser approaches. The Doctor warns Commander Vorsha to hold his fire and find out what they want, but is the level-headed commander one who'll listen?

With Silurians in control of the base, Icthar reveals his plan for a final solution to Earth's human problem, which presents the Doctor a great moral dilemma.

The TARDIS arrives in Little Hodcombe. Tegan wants to visit her grandfather, only he's disappeared. There's also a war game going on, and it's getting out of hand.

The Malus, an alien that's purely evil, needs the civil war re-enactments to become authentic so it can feed off the psychic energy of dying and embattled men and fully revive. Not if the Doctor can derail things, of course.

In the far flung future, the TARDIS is forced to crash land on the planet Frontios, where the Doctor finds some of the last surviving human beings cowering from a meteorite bombardment.

Following the destruction of the TARDIS, the only part of it left is the hat stand. So Turlough uses it as a weapon! Plantagenet gets swallowed by the earth, and Norna and Turlough discover the Tractators.

Trying to rescue the Doctor from the Tractator's trap, Tegan finds herself and the Doctor in even more trouble. Turlough goes a bit mad, and reckons he knows the evil of the Tractators from old.

The Doctor tries to deal with the Tractator's cunning plan, despite Turlough's best intervention. They discover the splintered TARDIS in the tunnels beneath the planet's surface, but how will they put it together again?

The Doctor and Peri get involved with drug running after landing on the twin planet of Androzani Minor and getting arrested as gun runners and targeted for execution. Not before Peri stumbles into some highly toxic and lethal plant life.

Having been saved from execution by Sharez Jek and his androids, Jek takes a shine to Peri, and wants her with him forever. Salateen tells the Dr and Peri that they are dying from Spectrox toxemia, but there is an antidote.

After escaping the vicious Magma creature, the Doctor is made a prisoner of the gun runners and taken to Androzani Major. The real Salateen takes an ill Peri back to Chellak.

Chellak and his men attack Jek's base. The Dr. crash-lands the ship, and must escape from his captors to find the antidote to the Spectrox poisoning and save Peri. He does so, but at a staggering cost.