Two thugs plan on stealing a set of famous pearls. They must be some popular gems, because elsewhere, other gangsters make similar plans. When safe crackers attack, the worried butler reports the theft to his boss, who seems to either be unconcerned, or at least something of an eccentric.
The thieves begin doing their best to fence the goods. The trouble is that the fence claims the gems are phoney, after he runs a fake test, and the con works. He ends up with the pearls. Are they really fake ones?
The disgruntled thugs have a fight, and there’s a bout of gunplay. Meanwhile, Blackie and Mary relax after talking about how they proved to the owner how easy it was to steal the pearls. Then Blackie realizes the pearls he has are also fakes.
Meanwhile, the owner talks to Blackie, who had also been fooled by the plan to keep the pearls safe, and reveals a secret passage in the safe, and the fact that he kept three sets of fakes there, while the real ones were kept separately. His entire elaborate plan is shared. Just when he is showing off, guess what turns up missing?
The once calm, cool, and collected owner starts to panic, especially when the real pearls have turned up in the hand of a dead man. Or have they? It’s up to Blackie to untangle the mess, and figure out what happened to the real pearls, and who took them.
With the word out about fake pearls, and real pearls, the various gangster factions who had a hand in stealing the gems now scramble to make sure theirs isn’t the real set. Bodies pile up. Blackie gets blamed. Farraday shares a bit of info that gives Blackie the clue he needs, and now it’s a matter of springing the trap on the real killer. After an altercation with the bad guys, Blackie reveals what tipped him off, and the details of the mystery are told.