Anne Cronin was pregnant with twins, a boy and a girl. During a difficult operation, Dr. Spencer R. Eliot, a friend of her husband Roger, was unable to save the girl.

To spare the parents’ feelings, Spencer told them that there had never been twins. The boy, Zaphie, survived and lived what seemed to be a normal life.

Eight years later, Roger calls Spencer and says something is wrong with Zaphie. Spencer goes to the Cronin mansion, only to find it abandoned.

He must explore the strange house and gather clues to uncover the mystery.