This clever, entirely unexpected delight weds a spy movie conceit to an observational documentary framework: Sergio is a dapper widower in his early eighties who gets hired by a private detective to go undercover in a nursing home to investigate whether a woman who lives there is being abused and robbed. Initially, Sergio, with his spy glasses and lack of tech savvy, cuts a conspicuous and amusing figure as he reports back to his no-nonsense boss. But like any great detective story, the solution to the mystery isn’t as important as what’s learned along the way, and Sergio forges poignant, sometimes heartbreaking bonds with an array of fascinating elderly women. Director Maite Alberdi’s camera captures interactions with remarkable intimacy and compassion, resulting in a warm, funny work of nonfiction with an emotional power that sneaks up on you.