Starring Sylvester Stallone and Arnold Schwarzenegger. Rated 14A. Now playing

If you’re still into watching movies with Sylvester Stallone and Arnold Schwarzenegger, Escape Plan offers you two geriatric musclemen for the price of one. Do we really care if Sly and Arnie are starting to look like a couple of He-Man action figures that have been left on the radiator for too long? Okay, so close-ups can get a little unsettling at times. But the bizarre novelty of the plot works hard to make up for the fact that both our leading men are a few decades past their prime.

Stallone plays security expert Ray Breslin, an escape artist whose specialty is breaking out of America’s toughest prisons, thereby exposing any inherent flaws. He’s hired by the government to face his biggest challenge yet: a high-tech, subterranean prison that houses the world’s worst criminals. So Breslin goes undercover, posing as an inmate with a terrorist background.

The prison’s flawless security and ruthless guards prove too much for Ray. But when Breslin reveals this true identity, he discovers that someone has paid to keep him incarcerated forever. The sadistic warden (nicely underplayed by Jim Caviezel) wants to use him to gather information on a mysterious figure known as Mannheim. Breslin’s other option? Figure out a way to escape from a prison that seems virtually escape-proof.

Breslin’s only ally is a wily inmate named Rottmayer (Schwarzenegger, who plunges into his role with mixed results). By the time we meet Rottmayer, we’re long past caring about the numerous logistical flaws in the script. We just want to see how the two of them are going to bust out of the place.

Director Mikael Håfström makes the most of a few clever twists and turns. It’s a good thing, too, since Stallone delivers his lines in the kind of droning monotone that suggests a punch-drunk Rocky Balboa. But then, if you’re looking for great acting, you’ve wandered into the wrong movie.

Still, the cast does its best to take things seriously. Silly quips are kept to a minimum. And there’s a dark atmosphere of foreboding that consistently bolsters a rather improbable premise.