"Blue Ruin" is a moody, stripped-down action thriller with the most unlikely vigilante one could imagine. Dwight (Macon Blair) is no buffed-up hero, but a soft and skittish loner who has no idea how to hold a gun, much less use it.

Before Dwight begins seeking justice, writer-director-cinematographer Jeremy Saulnier wants us to understand the kind of guy we’re dealing with.

The raw-edged indie, which won the Cannes FIPRESCI (International Federation of Film Critics) prize at the 2013 Directors’ Fortnight, opens in near silence and stays there for the first act.

Our first sighting of Dwight is of him barreling through a bathroom window: wet, naked, scraggly beard, uncut hair, grabbing clothes drying on the line to cover himself as he runs across backyards and the house’s unsuspecting residents head to the back door.

Dwight looks to be about 30, though as one of the homeless you see too often now it’s hard to tell. The camera follows him through his daily routine. When a local cop rousts him one morning, their conversation is the catalyst that snaps Dwight out of his daze.

‘BLUE RUIN’ Rated: R Opens Friday at Kahala 8

As with most things about "Blue Ruin," the reasons for the man’s sudden focus are cloaked in mystery. A newspaper headline offers a clue — a double-murder conviction overturned. It puts Dwight on the road, but where remains unknown.

"Blue Ruin" is an uneven film, and there are slip-ups along the way, but the tension that settles in slowly keeps you with it. The mayhem that is coming is much more refined than it was in Saulnier’s first feature, 2007’s "Murder Party," which also featured Blair, though not in a starring role.

The core of the film is a cat-and-mouse game. Outside a prison, Dwight hunches down in his blue Pontiac, keeping a careful watch. A stretch limo filled with members of what we will soon learn is the Cleland clan pulls close to the gate.

As Dwight follows the limo to a local bar where the family is celebrating, it becomes clear he has no idea what he is doing. And he’s terrified. Of the Clelands, yes, they’re a formidable bunch, but the fear seems more rooted in whether he can actually kill a man, even one who destroyed his life.

The rest of the film follows Dwight’s haphazard trail of destruction as he tries to exact revenge.

There is a Hatfields and McCoys-style feud going on between Dwight’s family and the Clelands. Most of it plays out in central Virginia, in many cases shot in the haunts where the filmmaker and his boyhood friend and the film’s star grew up.

Dwight’s sister Sam (Amy Hargreaves) and her two kids live in the lovely old Alexandria, Va., house that the filmmaker actually grew up in. It fits the tone of the film, but its choice was also an economic necessity for an indie on a shoestring budget.

Blair’s beard, like most of the film’s effects, is organic; the actor spent a year growing it. And it’s a shock when it is shaved. The bloody bits come as a shock, too. Though the director uses these moments sparingly, when the bullets fly and the knives cut, it gets gory and graphic fast.

One death starts a war. The Clelands are far better equipped for it than Dwight. The battle lines get clearer in the standoff between Dwight and Teddy Cleland (Kevin Kolack), one of the brothers of the man Dwight is driven to destroy.

The actors do their part to keeps things interesting and intense.

As with these sorts of feuds, there are major misunderstandings. Old secrets reveal new truths as they make their way to the surface, but they don’t stop the killing or the surprises in "Blue Ruin."

Review by Betsy Sharkey, Los Angeles Times