Perhaps the wizard had gone home... or perhaps the two transportations (one for him to get in and the other for the people to get out) used up all the power, and he slowly died of thirst. And regenerated... and died of thirst. And regenerated... and died of thirst... Man, that's really rough! Good writing, though, I really liked this story.
What a wonderful story: beautiful and melancholy. It really gets right to the heart of the Doctor's character.