On a cruise ship just returned from South America, Abbott (Trevor Bardette) the diamond merchant is preparing to disembark when there's a knock at his cabin door. When he answers it, he's shocked to see the criminal Cueball (Dick Wessel) there, demanding his stash of diamonds be handed over. Abbott pulls a gun on him, but to no avail and ends up strangled by Cueball's leather hatband, and the villain helps himself to the gems in the process. This is a case for Dick Tracy (Morgan Conway), but at the moment he's at home with the telephone off the hook thanks to his birthday party. But as ever, he must be called away to fight crime...
The second of the Morgan Conway Dick Tracy films, and the second in the RKO series, it was also his last. Although comic strip creator Chester Gould reputedly like the actor in the role, the public wanted to see Ralph Byrd back after the thirties serial and radio adventures, but in his defence Conway managed the straight ahead, morally uncomplicated detective role with efficiency. It's just that Tracy in this film is always a step behind the audience thanks to the script, by Dane Lussier and Robert E. Kent from Luci Ward's story, which tends to spell out the mystery to us before the hero twigs what is going on.
This means that whatever tension there is rests on whether Tracy can solve the crimes without any of him or his allies being harmed, and as that is a foregone conclusion there's not much exciting about this instalment. Cueball could have been more devious, but in effect is a brutal thug with a penchant for throttling whoever crosses him - at one point it seems as if he will bump off the whole of the bad guy cast before Tracy will even get the chance to arrest them. Finding someone to purchase those diamonds is top of his agenda, and to that end he gets involved with antique dealers; you never realised that the antiques business was such a hotbed of corruption.
Cueball also needs a place to live, so hides out in the basement of the colourfully-named Dripping Dagger bar (complete with neon sign of a, er, dripping dagger), which is owned by the equally memorably-named Filthy Flora (Esther Howard), a disreputable sort who is looking to get in on the diamond action, but gets more than she bargained for. Tracy doggedly follows the trail of corpses left in Cueball's wake, assisted by girlfriend Tess Trueheart (Anne Jeffreys) who naturally has to be landed in peril that only Tracy can save her from, and the fruity Vitamin Flintheart (Ian Keith doing his best John Barrymore) who adds a spot of humour. It's not bad, but more functional than inspired. A routine case for the detective. Music by Phil Ohman.