The story is told in flashback. Backers want a gambler to marry a rich girl for her dowry.

Celebrated as supersleuth, Mr. Moto comes out fighting when a brutal boxing match turns into cold-blooded murder! Assisted by detective-in-training Lee Chan, Moto sets out to track down the killer…

When a prominent official is murdered at a banquet honoring Charle Chan, the detective and son Lee team up to expose an opium-smuggling ring.