Amory Ames is enjoying the calm of her country house, Thornecrest, before the imminent arrival of her first child, while her husband, Milo, is away on business. Yet her period of relaxation is disrupted when a stranger appears on her doorstep, also claiming to be Milo's wife. Though Amory's marriage has had its ups and downs in the past, she is convinced the woman is mistaken. However, when a second unexpected visitor arrives, secret identities and whirlwind romances appear to be par for the course. Then, when a body is discovered, events take a sinister turn, and Amory resolves to uncover the killer in the crowd.