Jonathan shares an apartment with his night-working brother John, with whom he communicates only via daily video messages. Okay, it’s no spoiler — indeed the film’s central theme — to tell you that they occupy the same body. Their regimen, set up by psychiatrist Patricia Clarkson, works fine until John breaks a cardinal rule and gets a girlfriend. This intelligent and absorbing little sci-fi tale, an intriguing take on the dual-personality concept, gives Ansel Elgort (The Fault in Our Stars, Baby Driver) the chance to demonstrate his acting chops by deftly juggling two roles without disguises or makeup tricks. (95 min)