“Let Him Go,” starring Diane Lane and Kevin Costner as an aging rancher couple out to rescue their grandson from a clan of varmint in-laws, is set in Big Sky Country about 50 years ago, and it’s like a family-values, homespun-nostalgia version of “The Searchers” crossed with “Midsommar” on the range. If that sounds like an oddball of a movie, but one that’s going to keep you watching, it is. “Let Him Go” isn’t subtle, but as a genre film it’s original and shrewdly made, with a floridly gripping suspense. And Lane and Costner give it their all in a casual way that only pros this seasoned and gifted can. They turn the movie into an unlikely thing: a touchingly bone-weary romance steeped in vengeance.
At first, we think we’re watching a sensitive weeper-of-the-week about grief, loss, and time’s healing passage. Lane and Costner play Margaret and George Blackledge. He’s a retired lawman, with a badge and pistol in his drawer that look like they came out of an old Western (Costner always looks like he came out of an old Western — and that’s a compliment). She’s a tough but tender farm wife who used to break horses and now dribbles sugar icing on homemade cakes that look good enough to be on a Sara Lee box. They have a nice quiet life on their ranch in Montana, living with their son, James (Ryan Bruce), his wife, Lorna (Kayli Carter), and the couple’s infant son, Jimmy. All is well until James dies in a freak accident (he’s thrown from his horse).
Cut to three years later, when the widowed Lorna marries the polite, wholesome-looking Donnie (Will Brittain), who is not what he seems. On a trip into town, Margaret, who spies them from her car window, observes Donnie giving little Jimmy a slap for the crime of having dropped his ice cream; he then gives Lorna a harder slap. As if the abuse weren’t disturbing enough, days later, without so much as a goodbye, they’re gone. Donnie has taken them to move in with his family somewhere in North Dakota.
Margaret and George, aghast at the fate that now looms over their grandson, climb into their ancient Chevy station wagon (it looks like it’s from the ’40s) and embark on a road voyage to get him back. Tellingly, it’s Margaret, still haunted by the loss of her own son, who jump-starts the rescue odyssey. As George points out, she has no legal justification for trying to wrench a boy away from his mother, but she’s being driven by instinct; George goes along to protect her. As they drop into small towns and ask around, they keep hearing stories about Donnie’s family clan, the Weboys (pronounced wee-boys), who from the sound of it are some sort of strongarm cowboy dynasty from hell.
“Let Him Go” starts as a detective story, but it doesn’t take long for Margaret and George to find their way to the Weboy compound, at which point the movie becomes a rural Western gothic thriller. The actors playing the Weboys are juicy sordid fun, from Jeffrey Donovan as the “courtly” Bill to Will Brittain as the weaselly Donnie to the great Lesley Manville, in frosted blonde curls, going knowingly over-the-top as the chain-smoking, good-ol’-girl matriarch rube Blanche, who can make a pork-chop dinner sound as friendly as a hanging. The Weboys, in their huge ghostly gray farmhouse in the middle of nowhere, are all about power, which they think they have more of than anyone else. We think, “Oh, yeah? Just wait until Kevin Costner picks up that pistol.”
But the power, and slight surprise, of “Let Him Go” is that as staged by writer-director Thomas Bezucha (adapting Larry Watson’s 2013 novel), it’s not some glib shoot-’em-up fantasy. It’s a revenge-and-rescue action film that’s honest about the stakes of heroism. Lane and Costner make the Blackledges a couple at once affectionate and cantankerous, but by the end they’re united — in their mission, and in the sacrifice they’ll make for it. “Let Him Go” is basic, but it doesn’t let go.