With a title like that, Stranger in My Family carries the whiff of an airport-bookshop thriller, or a true-crime podcast, or one of those Harlan Coben-type Netflix series stuffed with vaguely recognisable faces who make terrible decisions at every turn. Surprisingly, it turns out not to be any of those things, but rather an emotionally intelligent and affecting one-off documentary about identity and belonging. Luke Davies is a 30-year-old man who grew up in Rochdale, thinking that his parents were his biological parents, and that he was white – until he did a DNA test to trace his heritage, and found far more questions than he did answers. Luke is clearly close to his mum and dad, Liz and Gary, both of whom appear throughout this film. Their son is a credit to them, and whenever they sit down to chat with him, they seem thoroughly lovely and understanding. But, Luke says, he always felt a little different. At 18, he came out as gay, thinking that might be what had been needling him. His parents were very supportive. Still, the feeling of difference persisted. Like millions of people, he sent off a DNA test to find out more about his roots; he says he assumed it would come back saying what he thought he knew already. There have been plenty of cases where ancestry websites have brought family secrets into the light. Often, these stories are so life-altering and cataclysmic that they make the news. In Canada recently, for example, two men in their 60s discovered they had been switched at birth. Luke finds that the answers didn’t quite match his expectations. Through the DNA testing website, he discovers that his breakdown suggests he is roughly a third Iberian, a quarter West African and a quarter English. “Well, how has this happened?” is what he thought after he read the breakdown. What follows is a fascinating story of heritage, family and love, with all of its complicated power and in all of its makeshift beauty. Luke finds out that when Liz was first getting together with Gary, she went on holiday to Portugal with her best friend Yvonne. In Portugal, she had a fling with a barman named Carlos. It barely lasted the holiday, and she has no idea where Carlos is now. When Luke was born, she says, as soon as she saw him, she knew that Carlos must have been his father. But nobody said anything about it, and life carried on, as life is wont to do. Luke’s boyfriend Sam looks at photographs of Luke as a baby and is incredulous that nobody thought to mention it. There is a warm and thoughtful subtlety to Luke’s voyage of discovery. It is part investigation, as he uses genealogy websites and experts to try to track down Carlos, which is no small task, given that all he has to go on is the first name and his mother’s 30-year-old memory of a man who worked in a bar. The investigation itself is not hugely dramatic, though it is remarkable to see people work their way through information to uncover mysteries that might once have been thought unsolvable. I also love Yvonne, who returns to the scene of the holiday in the hope that it might jog her memories of the bar where Carlos worked. “Ooh, I really recognise this,” she says, as she and Luke have a semi-awkward discussion about the realisation that they might be looking at the site of his conception. “I’ll piece that together, it’s fine,” he says, with barely a wince, as she starts to explain what happened there. But it also asks deeper questions about identity, and how family patterns may repeat themselves, and what it means to belong, and the many ways in which we can do so. Luke says that learning he was of West African descent and working out what that meant made him “feel like an impostor, in a way”. As the film goes on, he starts to look at himself in a different way. Liz and Gary have to grapple with their own feelings about Luke, Carlos and what could be uncovered in the investigation. Liz admits that she feels guilty about putting Luke through all this. “I wish I could put it right,” she says, in one of the many touching moments. Gary, meanwhile, is a typical northern dad, humorous, stoic, and full of love for his son. I won’t spoil it by revealing how Luke’s journey ends, but it is well worth watching this gentle film, which punches far above its weight, to find out.