Two buddies in the Korean War, one a bit of a wild card and the other a straight-laced soldier, have their lives changed during combat on a distant beach. When daredevil Vince (David Janssen, TV's The Fugitive) is wounded near the enemy lines, his brother-in-arms, Matt (Jeffrey Hunter, Star Trek's Captain Pike), risks his life to save him. When Matt is wounded in the process, Vince swears to make it up to him. Vince is determined to make a lot of money when they get back to America, and when he does, half of it is going to be allocated to paying back his savior.
Jump ahead several years, and Matt is living a life of boredom and disappointment. He survived his shooting, but has a plate in his head to show for it. He married Nina (Stella Stevens, The Nutty Professor), a beautiful blonde whose good looks are only overshadowed by her drinking problem. Matt would leave her if he could and take up with the caring secretary Liz (Elaine Devry, The Cheyenne Social Club) who he spends his evenings chatting with in parked cars. The only problem is that Matt is in hoc up to his eyeballs thanks to Nina, and he's beholden to her father, who also happens to be his boss. Dear ol' dad is a cheat and Matt knows it, ripping off his customers, but there's nothing Matt can do about it.
Then Vince re-enters Matt's life with a scheme to earn both men half-a-million dollars. Vince has been working for a foreign dignitary south of the border, and the diplomat had some jewels stolen from him. The ill-gotten cash those jewels earned is coming back across the border, and if Vince takes the initiative and robs the robbers, his boss will let him keep it. He wants Matt to be his driver, partners just like old times, and when the money is in, he'll give him 50% just as promised. Matt refuses at first, but Nina's vile nature is too much to bear. The money is his only way out.
This is the plot of Man-Trap, a wicked little crime picture directed by actor Edmond O'Brien (D.O.A., The Hitch-Hiker). Released in 1961, it's a bit outside of the film noir movement that dominated previous decades, and instead reflects changing social mores and post-1950s disappointment. Nina is a piece of work, as alluring as she is vicious. Stevens plays her with a dangerous electricity and unrelenting sexuality. She tears Matt down, playing with his emotions and his desires, and regularly pushes him to the edge. He barely stops short of violence. Vince turns out to be no better. Janssen is a firecracker, portraying the crook with a verve that borders on manic. Hunter's would-be hero is the perfect square-jawed lunkhead, stuck in between the two, conflicted about his own actions, and mostly ineffective as a result.
Given the nature of the picture, it's no surprise that the heist goes horribly wrong. O'Brien stages a pretty impressive gun battle that turns into a high-speed chase on the highways outside San Francisco. The bungled robbery is only the kindling to ignite Man-Trap's real fire, however; the film's final third is its strongest, with Matt, Vince, and Nina locked in a three-way melodrama. The fighting gets mean, and the consequences get drastic. Claws, quite literally, come out.
The only downside here is that O'Brien can't maintain the energy straight through to the end. Some of Man-Trap's final scenes feel a little unnecessary. After a scuffle with the men they robbed, Matt loses his memory, and some of what follows is both a little rushed and a little hokey. It ends up working thematically, though; in recovering his memory, he recovers who he is, and the one-time do-gooder learns how to do good again.