David Oyelowo, the soulful actor who played Martin Luther King Jr. in Selma a few years ago, deserves mainstream success if he wants it, and tossing off a few crowd-pleasing potboilers might seem like the way to get it. But while Don’t Let Go (called Relive at its Sundance premiere) starts with a perfectly good premise, it soon turns into a formulaic police procedural with the most obvious, easily guessed resolution. The hook is irresistible, though: LAPD detective Jack Radcliff (Oyelowo) is surprised to get a phone call from his recently murdered niece, Ashley (Storm Reid), calling from three days before she and her parents were killed. Uncle Jack eventually takes advantage of the time warp to try to prevent the murders, but not before spending a combined seven or eight minutes (or so it feels) staring agape at the caller ID. Writer-director Jacob Estes (whose Mean Creek and The Details were also Sundance debuts, which goes a long way toward explaining how this one made the cut), quickly loses interest in his sci-fi/fantasy conceit and defaults to disappointingly mundane dirty-cop, this-conspiracy-goes-all-the-way-to-the-top detective tropes that don’t do anyone any favors. Oyelowo is magnetic, though, even when stumbling around panicked and dumbfounded.