Chan’s testimony results in a death sentence for convicted murderer Steve McBirney (Marc Lawrence). However, he escapes and heads to a wax museum, a secret Mob hideout run by Dr. Cream (C. Henry Gordon). Cream, a crooked “facial surgeon”, operates on McBirney, changing his appearance.
Chan is lured to the wax museum on the pretext of sparring over an old case with Dr. Otto Von Brom (Michael Visaroff) on a radio broadcast arranged by Cream. Based on Von Brom’s testimony, Joe Rocke had been to be executed, but Chan is convinced that Rocke was innocent. In fact, it is all a setup so that McBirney can have his revenge, but Chan already suspects it. His son Jimmy (Victor Sen Yung) sneaks into the museum to investigate (without Chan’s knowledge).
When everyone gathers at the museum, Carter Lane barges in, representing Mrs. Joe Rocke. His client also sneaks in. When the principals gather around a table to reenact a scene from the Rocke case for the broadcast, Cream makes sure Chan is in the seat wired for an electrocution. However, Von Brom insists on changing seats. Museum night watchman Willie Fern is tricked into throwing the switch. The lights go out, and Von Brom dies … but not from electricity. (Lily Latimer, Cream’s assistant, had cut the wire in an attempt to keep the museum’s other function a secret.) Chan finds a small puncture wound in the dead man’s neck and a bamboo blowgun dart.
Chan becomes certain that “Butcher” Dagan framed Rocke, his business partner, and that he killed Von Brom as well. Dagan was supposedly murdered by McBirney, another business partner and a friend of Rocke’s. With Cream having operated on Dagan, no one knows who among those gathered at the museum is him (Jimmy even suspects Mrs. Rocke). Dagan kills McBirney and makes an attempt on Chan’s life, before the detective finally unmasks and captures him.