Twelve-year-old orphan Will Henry lives in the house of Dr. Pellinor Wortrop, a famous monsterologist and a mysterious man. Strange rumors circulate about their activities, and few believe that the doctor is interested only in medicine. One day, Wortrop learns that his best friend and colleague, John Chanter, has disappeared: while searching for a new species of monsters, he went into the wild lands and never returned. The indigenous people say that his soul now belongs to a wendigo, and that he himself — if he is alive at all — has stopped being human and has turned into a vampire. But Wortrop refuses to believe it and wants, no matter what, to save his friend.