Edward Chamberlayne is holding a cocktail party for his friends, mistress and an unknown guest - but where is his wife?
Faced with uncomfortable questions, Edward is forced to invent an excuse for Lavinia's absence in order to alleviate the curiosity of his friends. However, the unknown guest seems to know a great deal about the couple and quickly sets about analysing them.
But who is this mysterious man and how does he know so much about them? And is he truly unknown to them all?