Loosely based on the Amanda Knox story, Tom McCarthy’s “Stillwater” has an Oklahoma construction worker, Bill Baker (Matt Damon), determined to free his daughter, Allison (Abigail Breslin), from the French prison she has spent the last five years in. Similar to Knox, Allison is accused of gruesomely killing her girlfriend. Baker, a well-meaning working class yokel, arrives in France but can’t speak a word of French. Enter amateur actress Virginie (Camille Cottin) to help him navigate the maze-like murder-mystery. It helps that she also believes in his daughter’s innocence and together they try to find the witnesses and suspects to free her. Until then, McCarthy (“Spotlight,” “The Station Agent”) keeps our investment in the film with a firm grasp, but co-writers Thomas Bidegain, Noé Debré and Marcus Hinchey screenplay starts to lose its edge once Abigail is allowed to leave prison for the day, and implausible coincidences start to leak into the narrative. And yet, Damon’s chilled out intensity retains our attention throughout. The 50-year-old actor, one of the last true old-school star actors left, holds this wobbly house of cards together as the flawed MAGA dad trying to regain his daughter’s trust [B-]