12-year-old orphan Will Henry lives in the house of Doctor Pellinore Warthrop, a famous monstrologist and mysterious man. There are terrible rumors about their activities, and few people believe that the doctor is really only interested in medicine. One day, Warthrop learns about the disappearance of his best friend and colleague John Chanler, who, in search of a new type of monster, went into the wild lands and never returned. The Indians say that now his soul belongs to the Wendigo, and even if he himself is alive, he has ceased to be a man and turned into a vampire. But Warthrop refuses to believe this and wants to save his friend at all costs.