As “Tim” (Dave Franco) and his partner “Millie” (Alison Brie), whose relationship is showing signs of trouble, relocate to a secluded house in the countryside close to her new teaching post, things take an odd turn. While out walking, they stumble into what seems like a cave during a sudden downpour; it contains old benches and a strange painting. They find water inside, so at least they don’t get dehydrated before waking up and escaping. Everything appears fine initially, but then “Tim” discovers he can't control his own body while showering—he’s jerked around as if by an invisible force. This is only the beginning of their magnetic troubles, and soon they are struggling to understand what’s happening. When “Millie” visits a coworker, she—and the audience—start to piece things together… The film doesn't take itself seriously; there's some dark humor and a particularly uncomfortable scene in a restroom that might cause discomfort. The conclusion isn’t very satisfying; it just kind of fades away. However, there is more to the story than initially meets the eye, and Franco and Brie have good chemistry as they portray awkward, jerky movements, while the special effects are unsettling and work well. It takes a little while to get going, but once it does, it moves along at a brisk pace.

Source on TMDB