Mary Russell and Sherlock Holmes turn the Riviera upside-down to crack their most captivating case yet in the New York Times best-selling series that Lee Child called "the most sustained feat of imagination in mystery fiction today."

It's summertime on the Riviera, where the Jazz Age is busily reinventing the holiday delights of warm days on golden sand and cool nights on terraces and dance floors. Just up the coast lies a more traditional pleasure ground: Monte Carlo, where fortunes are won, lost, stolen, and hidden away.

So when Mary Russell and Sherlock Holmes happen across the Côte d'Azur in this summer of 1925, they find themselves pulled between the young and the old, hot sun and cool jazz, new friendships and old loyalties, childlike pleasures and very grownup sins....