While visiting Badgeworthy, the home of the Carslake family, Matthew Armitage experiences a strange and frightening vision in a mirror in his bedroom of a man with a scar strangling Sylvia Carslake.

Time passes, the First World War takes place, and then finally Matthew marries Sylvia Carslake. However, suffering badly from shell-shock, he nearly destroys his own marriage through an Othello-like jealousy and possessiveness, which threatens to destroy both him and Sylvia, until one night Matthew's vision of the man with the scar comes back to haunt him.