Parts: 4
Writer: Christopher Bailey
Airdates: 1 February 1982 - 9 February 1982
Production Code: 5Y

Doctor: fifth
Companions: Adric, Nyssa, Tegan

Creature Feature: Mara

Story: While Nyssa sleeps off a bout of mild mental disorientation in the TARDIS, the Doctor, Adric and Tegan set about exploring. They have come to the jungle planet of Deva Loka, a fertile paradise populated by the pacifistic and primitive Kinda - although they are perhaps not as primitive as they appear. While Tegan falls asleep under a set of chimes in the jungle, the Doctor and Adric find their way to a futuristic dome nestled within the foliage.

The dome is inhabited by a survey team studying the planet for possible colonization. Half their number have vanished mysteriously, and while the Doctor cultivates a friendship with the resident scientist, Todd, the other two distrust him - and one of them is on the verge of insanity. Tegan, meanwhile, has found herself in a nightmarish dream world populated by characters who debate her existence and try to drive her mad.

Tegan's mental torture finally forces her to submit to the beings in her dream world, and she agrees to let them borrow her form in the real world. When she awakens, she has been possessed by the Mara, an evil entity that feasts on the suffering of others. If the Mara's plans are not halted, not only will it destroy the dome, but it will cause the end of time on Deva Loka.