In this British character study, a lonely 27-year-old woman (Jessie Buckley) still living with her parents falls in love with a mysterious young man (Johnny Flynn) who’s suspected of having murdered several children on the small island where they live. The film covers thematic territory similar to that of Claude Chabrol’s Le Boucher (1970), though writer-director Michael Pearce isn’t interested in developing suspense as Chabrol was. For the most part, Pearce considers the emotional life of the fragile heroine, gradually revealing details about her past and bringing her risky behavior into focus. The leads deliver affecting, nuanced performances, which gives heft to the psychological insights; Flynn is particularly good, creating a character at once charismatic and opaque. Less compelling is the subplot concerning the heroine’s relationship with her overbearing mother,