Action films are rarely about more than big explosions and slow-motion shoot-outs. So it’s surprising when they even attempt to have a social conscience, something made all the more unexpected by the presence of Dwayne “The Rock” Johnson. “Snitch” has all the elements of the generic action thriller, but its unsparing portrayal of the criminal justice system, coupled with a pervasive sense of helpless desperation and a strong ensemble cast, keeps the film from delving too far into the grounds of silly blow-‘em-ups.

When unwitting drug dealer Jason (Rafi Gavron) is arrested, his estranged father John Matthews (Johnson) is devastated to learn that mandatory minimum sentencing laws mean he is likely to spend the remainder of his adolescence behind bars. Determined to get his son out, Matthews joins forces with an ex-con (Jon Bernthal) employee to land the high-profile arrests that will get his son a reduced sentence.

From the beginning, there’s a sense of grim helplessness that pervades “Snitch,” and it keeps the film from becoming overly flashy. Every step Matthews takes to help his son is hard-fought, and “Snitch” takes pleasure in backing its hero into a corner. Michael K. Williams and Benjamin Bratt are adequately intimidating as the drug kingpins Matthews is trying to take down, and even the film’s big action sequences aren’t played for triumph, but simple, brutal necessity.

Dwayne Johnson rarely gets a role this dramatically demanding, and even though his limited range occasionally chafes against “Snitch”’s screenplay, the film boasts his best performance to date. Johnson may not be the most emotive performer out there, but his brand of unyielding determination and steely gravitas is a comfortable fit. The rest of the cast does admirable work, especially an unrecognizable Barry Pepper as the DEA agent in charge of keeping Matthews safe and an icy Susan Sarandon as the prosecutor too distracted by higher political aspirations to remember the human side of her job.

Even though it manages to work in some well-placed jabs at the criminal justice system, “Snitch” isn’t especially subtle. Good intentions aside, the film sledgehammers its point home over and over again, and the script doesn’t even bother to mask its themes, letting its protagonist lay out everything the film is trying to say in a late-in-the-game groan-worthy moment.

Though “Snitch” isn’t well-suited to nuance, the film nails the desperation of a father without any options, and “Snitch”’s surprising social commentary is refreshing enough to excuse its obviousness. More than that, it’s a compelling story with a strong emotional hook and a well-cast ensemble. “Snitch” tries to be smarter than it is, and while it often struggles, it’s hard to fault the film for making an effort.