Kate is a 26-year-old riddled with anxiety and panic attacks who works for a local paper in Brixton, London, covering forgettably small stories. When she's assigned to write about the closing of the local lido (an outdoor pool and recreation center), she meets Rosemary, an 86-year-old widow who has swum there daily since it opened its doors when she was a child. It was here Rosemary fell in love with her husband, George; here that she's found communion during her marriage and since George's death. It has been a cornerstone in nearly every part of Rosemary's life. But when a local developer attempts to buy the center for a posh new apartment complex, Rosemary's fond memories and sense of community are under threat. As Kate dives deeper into it's history, with the help of a charming photographer, she pieces together a portrait of the pool, and a portrait of a singular woman, Rosemary.