When the Fourth Doctor takes Leela to visit an immense tree space station known as the Heligan Structure, little do they know that the tree has been asleep for centuries, dreaming of vengeance against a man in a blue box ... As the tree awakes, the Time Lord and his companion soon discover why they are such unwelcome guests. Author Philip Reeve puts his own unique spin on the Doctor, his terrifying alien enemies and time-travelling adventures.