London, 1924. Following several months abroad, Judge Dee Ren Jie has returned to the city to intercept a transaction between a Russian diplomat and a Japanese mercenary.

Aided by Lao She-the Watson to his Holmes-along with several other colorful characters, Dee stops the illicit sale of an extremely valuable "dragon-taming" mace. The mace's owner is a lovely Chinese businesswoman who thanks Dee for its retrieval by throwing a lavish dinner party. In attendance is British banking official A.G. Stephen, who argues with the group about the tenuous state of Chinese nationalism-and is then poisoned two days later. Dee knows this cannot be a coincidence, and suspects Stephen won't be the only victim.

Sure enough, a young Chinese communist of Lao's acquaintance is killed not long after-and a note with a strange symbol is found by his body. What could connect all these disparate, bizarre events?

It is once again up to Dee's brilliant investigative skills and Lao's well-meaning but often bumbling assistance to get to the bottom of the Railway Conspiracy before anyone else ends up on the chopping block.