When a mild retired rubber-stamp maker visits the Conciergerie with his wife and his worldly friend, he expects a quiet lesson in history. Instead, in the dark passage once called Straw Alley, he hears a rough, commanding voice issue from his own mouth-and cannot explain the phrase it speaks.
In the cellars he finds a scrap of paper hidden between stones. Its ink is faded, its date is 1721, and its handwriting is unmistakably his own. Experts confirm the paper's age and the signature-like strokes; soon he is convinced that some earlier self was betrayed, imprisoned, and left a treasure behind.
As he hunts for the truth, ordinary Paris turns uncanny: a wax mask, a portrait, a violet cat, and a name that surfaces from the past. His wife worries, his spiritualist friend theorizes, and someone else seems to be following the same trail. To claim the fortune-or the identity-he must discover what happened on a long-ago first of April.