The story of Kaze continues just a few days after he has rescued Kiku (in Kill the Shogun). The two are going to Osaka Castle to see if any of Kiku's family survived the war. A group of mysterious samurai pursues them. While avoiding these pursuers, Kaze meets with a peasant boy called Frog, who attaches himself to Kaze and Kiku. Before they reach Osaka they find a murdered Krishitan inspector. The authorities believe this and other inspectors were killed by Christians, but Kaze is not convinced this is true.

When he gets to Osaka Castle, Kaze becomes enmeshed with a panoply of forces all trying to gain power. This involves the widow of Hideyoshi, the late ruler, as well as the meaning of some special swords. Kaze meets his first Europeans and his observations about these first foreigners show deep insight into what brings them to Japan.

Kaze solves the mystery of the murdered inspectors, but his decisions from this point put him and the two children in mortal danger. Only audacity and bravery can save their lives.

This series was picked as one of the French "Grande Detectives" collections, and all books in the series can be read as a stand-alone mystery or part of a thrilling, multi-book epic.