We don't ever find out exactly what happens with Calum (Paul Mescal), the young father, whose 11-year-old daughter, Sophie (Frankie Corio), he's just taken on an end-of-the-summer holiday on a Turkish beach in Charlotte Wells' sublime debut feature, "Aftersun." But we do understand how he uses this trip as a way to let her know how much he loves her, no matter what else happens next (quite literally, actually, he writes a letter to her that says, heartbreakingly, "I love you very much. Never forget that.")