One of the bright spots of this movie season is the new domestic thriller “Let Him Go”. It’s a movie that at first glance may seem slow and old-fashioned, but upon further discovery proves to be a highly entertaining tale of family and survival. It sneaks up on you making this cinematic powder keg one of the year’s best experiences.

At the start of the film, we meet Margaret and George Blackledge (Diane Lane and Kevin Costner), a 1960’s Midwestern couple navigating life after their son James dies in a horse riding accident. She expresses grief through dominance and anger, while he is withdrawn and shut down. Both parties, though, find common ground in helping James’ widow, Lorna, raise their grandson. It’s a decent arrangement until Lorna meets and eventually marries someone new.

Lorna’s new husband, Donnie (Will Brittain), is a hothead who likes to publicly beat his bride and stepson, galvanizing Margaret even more to step in and protect her grandson. But doing so won’t be easy; Donnie comes from a long line of crazy and we meet every loose screw family member culminating with matriarch Blanche. She’s played by Lesley Manville (“Phantom Thread”) and her performance almost borders on parody at times, threatening to derail an otherwise engrossing film. Tensions rise between the two clans, with one side wanting to protect the innocent child from a wild step family he never asked for and the other side fighting to groom him as one of their treacherous own.

Writer-director Thomas Bezucha (“The Family Stone”) adapted “Let Him Go” from the novel of the same name and has built a slow-burn tale of revenge and hereditary complications. The film takes a hard turn two-thirds of the way in, making audiences wonder what type of film they’re actually seeing and with that welcome shift the signs are clear that “Let Him Go” isn’t looking to play things safe. Both acting leads are also essential to the film’s effectiveness. Diane Lane has the meatier role as the troubled Margaret, and she fully sinks her teeth into the character’s grief and regret, reminding us why she is one of our best working actresses. Not far behind is Kevin Costner, who doesn’t have as many big scenes as his partner, but does a great deal with his supporting turn. All of these ingredients make “Let Him Go” a worthwhile discovery for those looking for a suspenseful dose of entertainment.

Rating: A-

“Let Him Go” is now playing in limited release.