THE GUNMAN “Ow, my hip!”

THE BABY BOOMERS—previously known as the cohort that inherited a pretty sweet setup from the Greatest Generation, and currently known as the cohort that somehow managed to fuck everything up just in time for Gen Xers and millennials—are getting old. And there are a lot of them. In 1950, Americans over the age of 60 made up 12 percent of the population; by 2020, that will have nearly doubled, to 22 percent.

Which makes all those inexplicable Taken and Expendables movies a bit more explicable. As their audiences have gotten older, Hollywood's action heroes—once a job for youngsters who could move faster than anyone else—have aged up. The star of all three Taken movies, Liam Neeson, is 62. As for those Expendables: Sylvester Stallone is 68. Arnold Schwarzenegger is 67. Bruce Willis and Mel Gibson are 59. Harrison Ford is 72. Even the best and most vibrant of our current action series—I speak, of course, as always, of The Fast and the Furious films—might feature some cars drifting into handicapped spaces when its seventh film opens next month. Vin Diesel and Jason Statham are 47. Kurt Russell's 64. Dwayne Johnson, the spring chicken brought on board with Fast Five to inject some life into the series, is 42. Meanwhile, Robert Downey Jr., the lynchpin of this May's Avengers: Age of Ultron, is 49.

All of this helps explain why The Gunman exists. Plot-wise, it's exactly what you'd expect a movie called The Gunman to be about: A noble man is hunted down, forced to fight back using only his very particular, very violent set of skills. In this case, said noble man is Jim Terrier (Sean Penn, 54), a former mercenary who, tortured by past misdeeds, spends his time making sure the people of the Congo have fresh drinking water. Naturally, it's only a matter of time until Terrier's past comes back to haunt murder him. If only Terrier had some kind of way to fight back. If only Terrier was some kind of... gunman.

Directed by Taken's Pierre Morel, The Gunman lurches along, hitting big dumb action beats and cramming in bit parts for a bunch of great character actors, from Idris Elba and Javier Bardem to Ray Winstone and Mark Rylance. But in between all the head-shootings and neck-stabbings and eye-gougings and out-of-the-blue face-punchings, there's something more interesting: Unlike almost every other action hero, Terrier really does seem too old for this shit. Like most retirees, he just wants to enjoy his hobbies, maybe travel once in a while, and sleep with a girlfriend 20 years his junior (Jasmine Trinca). But in dispatching an army of bad guys, grumpy old Terrier learns his lifetime of hard living has wrecked his body. Suffering from an illness as a result of his mercenary work ("Oh no, you've shot too many guns," his doctor basically tells him, "you've got plaque in your brain"), Terrier's a shell of his former self. Each time he fires a gun, it makes his condition worse, so in the middle of action scenes, he'll get dizzy, or space out, or, like most retirees, just need a quick nap. Penn's otherwise charmless performance offers, at least, a sense of dismay at all of this—a sense of betrayal as his body and mind start to fail him.

That—turning an action movie into an aging movie—could have made for something pretty great. But The Gunman has too many of those big dumb action beats to hit; this is the kind of movie that, between brief spurts of moralizing about conditions in the Congo, features BMW getaways, a travel itinerary more exotic than 007's, and lines like, "He's gone—there's nothing you can do for him." (Penn helpfully grumbles that one after a character's brains have been exploded directly into the camera.) Somewhere in The Gunman, there's a movie about what it's like to get old and still want to kick some ass. But to either their credit or discredit, everyone involved has done a pretty good job hiding it.