Action movies about righteous revenge usually feature brawny, stentorian Schwarzeneggerian or Rockish types pummeling an army of bad guys in heroic fashion until all the villains lie in an unholy clump. Not so “Blue Ruin,” a little independent thriller from writer-director Jeremy Saulnier—and it’s all the better for it.

The protagonist is Dwight Evans (Macon Blair), who’s introduced as a scruffy, bearded derelict scavenging in dumpsters for food and living in an old blue Pontiac, the ruin of the title. But when he accidentally learns that a fellow named Will Cleland is being released from prison, he replaces the car battery and sets off for his hometown in Virginia, obviously with revenge on his mind.

What follows is a gruesome scene as Dwight follows Cleland to a bar from the prison gates and takes bloody action against him. He’s not terribly good at covering his tracks, though, and his frenzied departure—in Cleland’s car, no less—leaves the man’s entire clan in pursuit.

What becomes clear as the plot proceeds is that Dwight blamed Will for the deaths of his mother and father, and now fears that the whole clan—Teddy (Kevin Kolack), Kris (Eve Plumb), Carl (David W. Thompson) and Hope (Stacy Rock)—might skip going to the law and seek its own revenge by targeting not just him but his sister Sam (Amy Hargreaves) and her kids. So he cleans up in a “borrowed” bathroom, pilfers some preppy clothes, sends Sam and her family away, and takes up a defensive position at her house.

The ensuing encounter, which includes shovels, bows and arrows, is only the first in a series that involves not only the Clelands in various combinations, but Dwight’s old high school pal Ben Gaffney (Devin Ratray), a good-natured bar bouncer who’s also a gun enthusiast. Everything culminates in a final showdown at the remote Cleland homestead, which predictably ends with plenty of corpses strewn about, though one person leaves unharmed.

Saulnier’s script is nicely constructed, taking some unexpected turns while offering an effective series of tension-building sequences punctuated by outbursts of violent action. And his direction is equally assured. But the picture wouldn’t work as well as it does without Blair, an unimposing guy who makes Evans a singularly unlikely but appealing antihero who seems almost befuddled, and morally torn, by the cycle of killing into which he’s been inexorably drawn. If the part were played by a typically invincible he-man type, the plot would have degenerated into the squalid simplemindedness of most such tales of vengeance. But by making Dwight an ordinary guy caught up in mayhem he’s unprepared for and unsuited to, Saulnier and Blair give the film shadings that undercut and toy with the conventions of the genre.

The remainder of the cast acquit themselves admirably, with pride of place undoubtedly going to Ratray, a bearlike fellow with a genial spirit who makes Gaffney enormously likable in spite of his willingness to settle matters with a gun. Fans of retro television will also appreciate seeing Plumb, a former member of the Brady clan, in far more formidable form as one of the unforgiving Clelands.

“Blue Ruin” is clearly a modestly-budgeted affair, but Saulnier, who serves as his own cinematographer, has used his meager resources well, making a virtue of necessity via compositions that keep the viewer off-balance. Other strengths include Julia Bloch’s editing, which brings the film in at a crisp ninety minutes, and the atmospheric score by Brooke and Will Blair.

This is an auspicious piece of work–a tight, taut, suspenseful little thriller that reminds one of the Coens’ early triumph “Blood Simple,” though without quite matching it.