A middle-aged man and his wife find their leisurely vacation routine uncomfortably compromised by the appearance of a former classmate and his curiously young girlfriend. For the past twelve years, Helmut and his wife Sabine have spent their holidays at Lake Constance. As the lazy days of summer roll by, Helmut bird watches and Sabine swims. At night they dine together, eventually retiring to bed with a good book and the promise of another relaxing day on the lake. But this year, Helmut has a chance run in with his former classmate Klaus. Of course it would be all well and good if the Helmut and Klaus were simply able to reminisce about their childhoods together, but Klaus is never far away from his enchanting, and far-too-young girlfriend Hel. Over the course of the next few days, Klaus finds every excuse possible to stop by and pay his old friend a visit. Helmut can't help but being annoyed by the obvious comparisons as the two couples spend more time together than he would like. Later, as the mismatched quartet sets out on a sailing trip, a sudden squall blows away the thin veneer of amicability, prompting everyone aboard to come clean about their true feelings.