The Doctor and Martha land on the planet Geravalon, where a spaceship is about to crash. They head towards a castle that the ship will probably overshoot, to land in the forest behind. They meet a chameleon, which is startled by the crash. They find the wreckage of an escape pod, a young girl and a man beside it. The man is bleeding badly. The girl is trying to dress the wound. An elderly man appears. He confirms the girl is a servant and the man is Prince Rodrique, heir to the premiership of the Majullion Confederation and introduces himself as Padros.The girl says that her name is Sastra. Martha realises that she is in shock.
In the castle Sastra begins to recover. Rodrique receives medical attention. Sastra tells Martha that there will be a celebration for Rodrique tomorrow. Rodrique invites Martha and the Doctor. He learns that Sastra saved his life and invites her too. However, her legs hurt and she worries that she may not be able to attend.
The celebration commences and Sastra attends, dancing with Rodrique. The Doctor has given her painkillers to allow her time at the ball, but they begin to wear off and Sastra flees. The Doctor, Martha and Rodrique follow, only to find her lying in a corridor. Her legs are green and scaled. The Doctor says she is one of the chameleons from the forest. Her body is trying to change back, but does not have enough genetic material to allow her to maintain human form. Rodrique kisses her, transferring genetic information to her body through saliva. The Doctor says that he must kiss her every twenty-four hours to maintain her human form. He and Martha leave.
- When Padros says that old men do not like change, the Doctor simply replies "tell me about it".