In Shangai, the "Green Dragon" threatens to kill Herbert Aboody, a rich exporter, unless he pays him 50,000 dollars. One of Aboody's secretaries calls inspector Wens for help. An amazing fact occurs, Wens kills Aboody and then disappears. What is the key to this mystery?

Commissioner Malaise investigates a strange crime: a mannequin, stolen from the window of a tailor, is found stabbed... But his face of wax has the features of a certain Gilbert, who died a year earlier in a family, all of whose members will become more or less suspicious to the Commissioner. He thinks that, in spite of Dr. Furnelle's conclusions, Gilbert's death was not natural. But finding the cause of death and the identity of the possible culprit will require more than a mere intuition.