The railway conspiracy

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?