Doctor Who: The Twin Dilemma
The Doctor has regenerated and all is not well. Confused, angry and acting strangely, the Doctor decides to become a hermit, so takes his concerned companion Peri to a desolate asteroid where he plans to live for several centuries.
The time travelers soon uncover a plot that threatens the entire galaxy. But why has an alien gastropod kidnapped twin boys from Earth, and will the Doctor recover in time to find out?