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Israeli-born writer-director Guy Nattiv and his wife and producing partner, actress Jaime Ray Newman, won the live-action short film Oscar earlier this year for “Skin,” a racially-based revenge story about a white nationalist whose young son reacts rather badly when his father returns home with his skin colored black by friends of a man he had brutalized. It was praised, one supposes, for its message about the insidious effects of racism, rather than for its coarse narrative and crude production.

This feature-length film by Nattiv is not an expansion of the earlier work, for which one can be grateful—though uneven and somewhat ragged technically, it represents a significant improvement on the short. To be sure it too deals with a bigoted skinhead, but it is based on the life of an actual person, Bryon Widner, who was a member of a Midwestern white supremacist group for years until he renounced their ideology—and suffered the consequences of his perceived betrayal. His story was previously told in Bill Brummell’s 2011 documentary “Erasing Hate.”

That title here refers to Widner’s decision to have his racist facial tattoos removed as a sign of his total rejection of his past—a long and terribly painful process that becomes a motif here, scenes of the operations intersecting with sequences dramatizing Widner’s development from hatred to love, and thus a symbol of the difficulty of his redemption.

There are two people integral to the change in Widner’s attitude. One is Julie (Danielle Macdonald), a single mother who, like Widner, is part of the so-called Vinlanders Social Club, a group of skinhead thugs run by Bill “Hammer” Krager (Bill Camp) and his wife Shareen (Vera Farmiga). Widner grows protective of her and her three daughters Desiree (Zoe Colletti), Sierra (Kyle Rogers) and Iggy (Colbi Gannett), and when she draws away from the group, he is moved to follow. The other is Daryl Jenkins (Mick Colter), a black activist who detects the sliver of doubt about the Kramers in Widner and makes it his goal to help the man extricate himself from the group’s malignant influence.

Precisely how Widner got involved with the Vinlanders in the first place is not covered here; when we are introduced to him, in the person of Jamie Bell, he is already a full, very active follower, ferociously brutalizing those identified by Kramer as enemies. Nattiv gives us a glimpse of how he would have been recruited by showing Bill and Shareen picking up a homeless teen named Gavin (Russell Posner) and indoctrinating him—a reflection, one presumes, of their usual practice.

But “Skin” is not about how Widner joined the Vinlanders, but how he left it—and the ramifications when Krager’s thugs come after him. The plot turns quite melodramatic in the latter stages, and one might wonder whether the actual events have been embellished to some degree, but Mary Lena Colston’s gritty production design and the frantic hand-held camerawork by Arnaud Potier go far to keep it grounded in reality, or at least a convincing approximation of it.

The other element of the film that does so is the acting. Pride of place has to go to Bell, who is fast becoming one of the screen’s most reliable actors. His turn here is about as far a cry from sweet Billy Elliot as one can imagine, a startlingly intense portrait of a man desperate to redeem himself for his brutal past.

It’s difficult to imagine “Skin” without Bell, but Macdonald’s contribution is no less remarkable. Julie is no more conventionally heroic a character than Bryon, but like him she showed extraordinary courage in disengaging from the Vinlanders, and Macdonald conveys that. Camp and Farmiga make a deeply unsettling pair, though they remain relatively undefined; she adds some sexual underpinnings to her relationship with their younger followers that make Shareen even creepier. Widner himself appears briefly in the closing credits, emphasizing the story’s real-life basis. That was perhaps an unwise choice, as it adds a documentary touch that deflates the dramatic impact of what’s preceded it.

Like Tony Kaye’s 1998 “American History X,” “Skin” tells a bracing story about one man’s struggle to free himself from the poison of racist ideology, anchored by an utterly committed lead performance. And, of course, the present direction of the nation’s politics makes the tale even timelier today.