Tod von Freunden (2021)

Set on one of Denmark's Oxen Islands, two couples, Sabine and Bernd, and Jakob and Charlie, live a carefree life with their teenage children, Karl and Kjell, and Emile and Cecile respectively. But when Jakob's brother Jonas returns after he disappeared 15 years ago, the kids fall under his spell. With the parents increasingly worried over Jonas' influence, the unthinkable happens - Kjell falls overboard while on a sailing trip with Jakob and Charlie and disappears without a trace.