Amory Ames is contentedly preparing for the arrival of her baby at Thornecrest while Milo, her husband, is away on business. But then a woman appears on her doorstep, also claiming to be Mrs. Ames, Milo's wife.

Amory's marriage has had its ups and downs, but her faith in Milo has been restored. Though the supposed second Mrs. Ames seems earnest, Amory is convinced she must be mistaken. However, when a second unexpected visitor arrives, and secret identities and whirlwind romances culminate with the discovery of a body, the characters appearing in town begin to seem more sinister, and Amory is determined to uncover a killer in the crowd.