A potent image in the riveting movie "Let Him Go" features Diane Lane standing at the left of the screen, clutching a young boy to her chest, while Lesley Manville moves in from the right, trapping him between the women's torsos.

That visualizes the conflict in this adaptation of the Larry Watson novel that was published by Minneapolis' Milkweed Editions. The boy is Margaret's grandson, the child of her late son, but his mom, Lorna, remarried and disappeared. Margaret and her husband, George (Kevin Costner), have tracked them to a remote enclave in 1960s North Dakota.

It's the home of new step-grandparent Blanche, and Manville, in the sort of showy performance that wins supporting actress Oscars, presides over it with an exaggerated friendliness that feels like she studied how genuinely nice people might act so she could use it to cover her hostility and contempt. Eventually, it all comes out.

"Lorna said you were rough bark," Blanche informs George at a tense dinner, turning to Margaret. "And I can see you're no day at the races, ma'am."

It's as if both women are staking their claim to the child, and in fact, that's what's happening. Like Watson's tense, spare novel, the movie's action is driven by character. There are long silences during which Margaret and George telegraph their worries about their mission or Blanche wordlessly lets Margaret know there is no way in hell she is walking out of there with their grandson.

From the get-go, "Let Him Go" has a mournful inevitability that suggests characters trapped by a dilemma with no good solution. We're on Margaret's side, but we also know she wasn't as kind to Lorna as she could have been and it might have made a difference if she'd made an effort. George supports his wife the minute she announces her intentions, but there's also a tender, ominous moment when she's asleep and he whispers in her ear, "Go home, go home."

It makes for an unusually quiet movie, one that is faithful to the novel but not easy to grab hold of. Its pleasures are almost contemplative, and although there is plenty of action, the real meat of the movie is the action in the characters' heads. Writer/director Thomas Bezucha was smart to cast actors who've already been married on screen (in the most recent Superman movies), actors who can say a lot with a glance, as Lane does when a disbelieving Lorna asks Margaret, "You want me to give up my son?" Playing across Lane's face are a stew of thoughts about the wrongness of separating mother from child and the rightness of her quest.

Bezucha makes a lot of smart, simple choices. He uses majestic vistas (the movie was shot in Canada) to underline the pure dignity of Margaret and George, but his staging of the climax, in a cramped hotel room, is clear and suspenseful. He was smart to cast Manville, whose theatrical gusto is nothing like the plain-spokenness of Lane and Costner, because that helps establish that they've stumbled into a world where they do not belong.

The movie is accompanied by Michael Giacchino's achy, mostly piano-based score. As it builds toward the finale, the music gets richer but Giacchino ends the movie on one perfect note that encapsulates the mood of "Let Him Go": a high, unsettling one.

Chris Hewitt • 612-673-4367