Harry is dead. Having left him abandoned and alone in pre-war Britain, the Doctor and Sarah try to solve the mystery of his death. But the only witness is in a lunatic asylum, driven mad by what he has seen. He tells of murder and mutilation, of living trees and long-dead legends, of wolfmen and war...And of a mysterious stranger known only as the Doctor. Can it be true that Harry discovered the last resting place of the Holy Grail? Why are the flowers and trees in a Somerset village in full bloom at Christmas? And is it just a coincidence that Harry died under a full moon? This adventure features the Fourth and Eighth Doctors, Sarah Jane and Harry.