Karra invites Ace to join her and the girl runs off with the Cheetah to hunt. The Doctor follows.
Midge has returned to his flat in Perivale. The Master continues to suppress the animal influence within himself.
Karra and Ace find horses. Although Ace wavers, she joins Karra for a hunt. When Karra stops to eat a dead animal, Ace remembers that the Cheetahs eat people as well. She is about to eat with Karra when the Doctor stops her. She returns to him, able to overcome the animal influence for a while.
The Doctor brings Ace back to the others and she is able to bring them back to Perivale. When they get back, the animal influence fades. Patterson believes he hallucinated the entire thing.
The Master and Midge join forces. Midge steals a motorcycle and then goes to the Youth Club to persuade the others to follow him and the Master.
The Doctor and Ace go to Midge's flat and find his sister crying over a cat killed by the Master. Ace falls under the animal influence again and realizes that the Master is at the Youth Club.
When Patterson returns to the Youth Club, Midge kills him in front of the others. The Doctor and Ace arrive too late but follow Midge to the park.
There they find a motorcycle waiting. Midge appears on another cycle with his followers. Ace wants to challenge him, but the Doctor, fearing she will change into an animal for good, goes in her place. The cycles race toward each other and collide, exploding in a fireball.
Midge is wounded and dies after the Master tells him he is too weak to live. Ace, determined not to fight, can only call for help. When she does, Karra appears and chases off Midge's followers. The Master challenges her and stabs her to death with the tooth Midge killed with. He leaves, spotting the Doctor alive in a rubbish pile, having being thrown from the explosion.
Ace goes to Karra's aide and finds she has turned back into a human. She dies in Ace's arms.
The Doctor finds the Master trying to break into the TARDIS. The Master boasts that he at last controls the animal power. He attacks the Doctor and they transport to the Cheetah planet, which is finally destroying itself. They fight but the Doctor stops before he kills the Master, realizing that it if they continue to fight, they will die. The Master tries to kill him, but he is transported back to TARDIS.
A Cheetah appears on the hill and takes Karra's and Midge's bodies. The Doctor returns and tells Ace that the Cheetahs will move to a different planet. He tells Ace that the planet will always live within her. They decide to go off into the TARDIS to new adventures…