When the Countess Narona meets Agnes Lockwood, the woman jilted by her fiancé, she feels a great sense of foreboding. After Countess Narona's marriage, she moves with her husband, Lord Montbarry, to Venice. There, disowned by his family, the lord apparently becomes a recluse and falls fatally ill. As much as Agnes tries to forget the episode of her broken engagement, her fate and that of the countess seem to be inextricably woven. Both are relentlessly drawn to the Palace Hotel in Venice for a final and dramatic encounter in the room where more than past emotions resurface to haunt them.

Loosely based on a case from the annals of French crime, the scene, scenery, players, conflicts, and especially the horror of this mystery come through the invention of one of our classic novelists.