Faunce is hired to prove the innocence of Lady Perivale, a rich young widow, whose reputation has been ruined by Colonel Rannock, whom she has refused in marriage. He claims she travelled to Algiers with him and lived with him as his mistress. As a consequence of the rumours, and witnesses who saw the woman in Algiers say she looked just like her, Lady Perivale has been cast out of society, and even the man she loves, a novelist called Arthur Haldene, believes the worst of her. In the meantime Rannock has gone missing, and may have been murdered. In the course of his investigation Faunce discovers the identity of the mysterious woman who was living with Rannock, and plots an elaborate scheme to clear Lady Perivale's reputation.