AllMovie

One is Guilty was an entry in Columbia's "Inspector Trent" mysteries, all starring the ubiquitous Ralph Bellamy. A philandering prizefighter is murdered, and then the prizefighter's manager is likewise bumped off. All evidence points to heroine Sally (Shirley Grey), but Inspector Trent isn't about to put the cuffs on her until he has all the evidence. Sure enough, the killer turns out to be the proverbial least likely suspect, whom the viewer will probably tag the minute the guilty party shows up on screen. As Trent, Ralph Bellamy is far more plausible and far less imbecilic than he'd be in Columbia's "Ellery Queen" series of the early 1940s.