After a good start, this crime drama gets bogged down from time to time, and ends up being just average, or perhaps slightly above average. Besides the interesting story setup, it features a good core cast, with Claire Trevor getting a good role that allows her to play a variety of material, Raymond Burr well-cast as a brutish villain, and Fred MacMurray.
The story starts with Trevor as a police officer working undercover in Mexico. Her initial dealings with Burr and MacMurray set up some interesting possibilities, and create some suspense from the start. The rest of the story is not really bad, but it too often allows the pace to stagnate, and it does not make the best use of some of the possibilities. Aside from a couple of good scenes, it plays out in a more routine fashion.
"Borderline" is still worth seeing for fans of the genre. Besides the main story, it has some occasional comic touches that come across all right. If it ends up seeming like a bit of a disappointment, it is simply because it showed signs of becoming something better than it turned out to be.