The Doctor, Crystal, Jason and Zog have landed on the leisure world of Krennos. They land outside the dome and have to fight sucking mud and moving trees to get there. While they struggle, the Manager watches them on screen with Susie. They have been investigating disappearances for weeks, and Susie thinks they should investigate. The Manager is too weak to make a decision, so Susie sends two people out.
The two rescuers reach the travellers and rescue Crystal, Jason and Zog, but the Doctor has disappeared beneath the mud. Safe inside the dome, but locked up, Jason and Crystal discuss the Doctor; the Manager watches on screen, and he, Gerry and Susie wonder if it's the same "Doctor" they have met before. To avoid suspicion, the Manager has them released.
All cleaned up, the trio sit in the ballroom, eating and listening to music. The food is bad and the musicians are out of key (and clumsy). Zog sneaks off and finds the swimming pool, but what he sees there terrifies him and he runs away screaming. The Manager sees this, and decides Zog needs to be killed. Zog is chased by Susie and Gerry, and runs into Jason. The Manager now wants them all killed.
Two of the Happy Campers sneak into Crystal's room as she sleeps and blast away at her. As the Manager watches on screen, he is confronted by the Doctor, who has finally broken free of the planet and made his way into the dome. He pretends he knows what the Manager is up to, but before the Manager can explain, Gerry and Susie enter and say that it wasn't Crystal that was killed, it was Madeleine. The Manager rescinds the order to kill the Doctor's companions, and begins to explain.
Meanwhile, Crystal wakes in the swimming pool. There is no water, but she is surrounded by bodies. At first she thinks they're dead, but they're just unconscious. She notices a white band on her arm, and rips it off. She meets up with Jason, who is almost hypnotised by a ball of light. He tries to leave the dome, but Crystal tackles him and he snaps out of it. Suddenly, a plant from outside begins to break down the dome wall.
The Doctor learns that the Manager and the other Happy Campers are Chameleons. They have sent away the scientists and kept the managerial staff. Unfortunately, they don't know how to take care of the planet, and it is now attacking the dome. They haven't fed the planet, and it has been absorbing people that leave the dome (by following the ball of light).
The Doctor tries to communicate telepathically with Krennos, as he did when he was under the mud, but he can't reach it. The dome wall is being broken everywhere, and plant tendrils are grabbing Chameleons and others alike.
In his office, the Manager, who was using Blade the last time he met the Doctor, makes a decision. He converts himself to one of the plants, and the attack stops.
The Doctor tells the Chameleons that they will have to be "deprocessed". He tells them the Manager put Krennos into a kind of coma. He talks to the real staff, and tells them that Krennos must be evacuated. The TARDIS crew leaves, with Zog planning his takeover of the universe.
- The builders of Leisure world are aware of the Time Lords and the Doctor invokes their authority as a threat.
- Zog is secretly an Aldeberian tyrant planning to enslave the universe.
- While the Doctor is believed to be dead, Crystal dreams that he has changed into either a taller man or a man in a Greenpeace shirt. This is a nod to the other two versions of the Doctor during the run of the stage play The Ultimate Adventure.
- The Chameleons landed on Krennos after the Second Doctor forced them to leave Earth and return to their own planet. (TV: The Faceless Ones)
- The Chameleon who took the form of the Leisureworld Manager formerly impersonated the pilot Captain Blade. (TV: The Faceless Ones)