A woman named Anne Cronin was pregnant with twins, a boy and a girl. Dr. Spencer R. Eliot, a good friend of her husband Roger, was unable to save the girl during a difficult operation. In an attempt to spare the parents' feelings, Spencer told them that there were no twins in the first place. The boy, Zaphie, survived and enjoyed a seemingly normal life.

However, eight years later Spencer receives a call from Roger, who tells him that something is wrong with Zaphie. Spencer hurries to the Cronin's mansion, but finds it abandoned. He has to explore the strange house and find clues that would help him to get to the bottom of the mystery.