Mercy Watts travels to Paris, but there's darkness in the City of Light.

The Fibonacci family saved Mercy's life at Cairngorms Castle and now she owes them a favor. Calpurnia Fibonacci makes it clear that it's time to make good. When you're dealing with a powerful mafia family, refusing isn't an option, but the case isn't going to be easy.

Mercy's job is to find a woman in Paris, one of the largest cities in the world. Angela Riley was married to the Fibonacci's accountant, a man who knows where all the bodies are buried, but she disappeared six years ago and was presumed murdered by a man she met in a bar. Her husband and family moved on until Angela's sister goes on vacation in Paris and gets a glimpse of her murdered sister on the fashionable Rue Cler. The Fibonnaccis want to know exactly why a woman from their inner circle would choose to disappear and Mercy's well aware that Angela's life depends on the answer.

To make matters worse, Chuck and Aaron tag along and they have agendas of their own. With the mafia and the shadowy Klinefeld Group involved, finding the wife of Riley will be much more dangerous than Mercy ever expected.