Copshop, which tells the story of a loudmouthed con man trapped in a podunk cellblock alongside an assassin who’s gunning for him, is a bit of a disappointment despite stellar performances by stars Gerard Butler, Frank Grillo and Alexis Louder that keep it interesting even when the plot slows to an unnecessary crawl.

Teddy Murretto (Grillo) is a greasy fixer for the Vegas mob. He never stops talking. It usually gets him out of trouble. But now, miles from civilization, it’s only digging him deeper into an anonymous desert burial. Grillo’s known for his action roles (many with Copshop director Joe Carnahan), and Murretto is a different sort of turn of him. It’s a welcome one. The actor took to social media recently to express that much of his character work was cut from the final edit, but he’s still a highlight. Maybe the highlight. Of all the characters, Murretto is the one with the most ambiguity and the most well-fleshed humanity … or lack thereof.

Butler, on the other hand, isn’t given a whole lot to do despite playing a flavorful bounty hunter stalking his prey. His Bob Viddick has a little bit in common with the actors’ grisly turn in Den of Thieves, but with more control. His performance is reliably good as a patient professional just waiting for the opportune moment to claim his prize.

It would be wrong not to mention Louder, though, who plays Valerie Young, a rookie cop with a love for antique firearms who ends up trapped between Muretto and Viddick. She serves her role in the story as the unambiguous hero. It’s thankless, but she’s good, too.

Unfortunately the script — written by Carnahan and Kurt McLeod, with an additional story credit from Mark Williams — sidetracks once the action starts. It simply doesn’t feel like the two big stars have a lot of interesting material in the second act. Anthony Lamb (Toby Huss), another assassin, shows up just when things at the police station can’t possibly get any worse. He traps our main trio in the cellblock. Huss’s over-the-top performance isn’t bad, per se, but it upstages the simmering tension within the cellblock itself. Removing the main tension of the film from Grillo and Butler feels like a mistake even while watching the film. These two are, frankly, titans of a certain genre of low-budget, often direct-to-DVD / VOD fare, and their dramatic sparring is the main ticket.

Still, there are pleasures to be had here. It operates on the logic, and with the same pacing, as a dime-store cops-and-robbers thriller. As the story unfolds, double-crosses and triple-crosses abound. It slows down unnecessarily in the middle, but the final confrontations are reasonably full of bullets and explosions. Copshop isn’t particularly great or particularly bad. It is, I guess, functionally entertaining for an afternoon of mad violence and verbal sparring from familiar actors. Just not what I’d hoped to see from such a stellar cast and talent.