One day Sarah Jane reads a book about a haunted house, Ashen Hill Manor. Rani, Clyde and Sarah Jane want to investigate. Luke doesn't believe in ghost and rather likes to stay at home doing his homework. At Ashen Hill Manor Sarah Jane, Rani and Clyde meet Toby Silverman, who works as a scientist. Then they suddenly see a man on the stairs. Clyde wonders if the man is a ghost, but Sarah Jane tell him that ghosts do not exist. Later Sarah Jane finds a book which includes an old picture of the man, which reveals his name, Erasmus Darkening. Shortly afterwards Rani and Clyde find the secret room of Erasmus Darkening. They see a mysterious machine, which according to Rani looks futuristic but not ghostly. After this Erasmus Darkening appears. He tells Rani and Clyde that for centuries he had tried to leave the house. Sarah Jane hears this and asks Erasmus Darkening what has stopped him from leaving. Erasmus explains that he is an alien and that he came to this house hundreds of years ago. His machine would take him anywhere but it's broken. Sarah tells Erasmus that she can fix his machine, but before that she want's to know why the strange things are happening in this house. Erasmus explains that it wasn't a ghost, it was him. He likes to read books, watch the fountain and hear the bells. Furthermore, he had to do something while he was stuck in Ashen Hill Manor. Then Sarah Jane repairs the machine and Erasmus can leave Ashen Hill Manor. His lasts words are "Free at last". Toby says to Sarah Jane that he doesn't believe in ghosts any longer but does believe in aliens. Sarah Jane added that she doesn't think Erasmus would ever come back as he had been stuck in Ashen Hill Manor for long enough.
Erasmus Darkening hasn't kidnapped any humans. He is just an alien who's stuck on Earth after his machine has been broken. He tried to return home, but hasn't harmed anyone. Sarah Jane fixes his machine and Erasmus leaves with the words "free at last".