As Panna dies, Karuna breaks from Aris's influence and returns to the cave. Panna's memories and knowledge have passed to her.
Karuna explains that the Mara emerge from the dark places of the inside to the real world. The Doctor realizes it must have come through Tegan.
Adric, fed up with the childish games of Sanders and Hindle, runs out.
The Doctor finds Tegan under the wind chimes, which Karuna explains are extremely dangerous for someone on their own. The Doctor wakes Tegan and asks her what happened.
Aris has the Kinda construct a survival suit out of branches and leaves.
Tegan reluctantly tells the Doctor about her dreams and confirms his suspicions about the Mara.
Adric emerges from the dome in the survival suit. Aris orders the Kinda to attack and they flee as it begins to fire wildly, fed by Adric's fear. The Doctor finally calms Adric down and extracts him from the suit.
Adric tells them about Hindle and the Doctor and Todd race into the dome. They find the two men playing within their city. Hindle explains that the Kinda obey him because they think he's captured their souls in his mirror.
When the Doctor accidently steps on one of the people in the toy city, Hindle goes mad. In the struggle, the mirror is broken and the Kinda leave. Hindle tries to operate the explosives but Todd gets him to open the Box of Jhana. He is quickly overwhelmed by it.
The Doctor realizes that the one thing evil can not face it itself. He has Adric gather solar panels. He and the Kinda create a circle of the mirrored surfaces to trap and destroy the Mara.
Karuna leads the wounded Aris into the circle. The Mara detaches itself from Aris and he is dragged to safety. The snake swells to immense size. Tegan is horrified that she had it within her mind. The Mara quickly weakens and vanishes.
Hindle and Sanders are now cured of their illness. Todd intends to tell Earth the planet is unsuitable for colonization. The Doctor returns to the TARDIS, where Nyssa has recovered.