It Comes at Night Joel Edgerton, Christopher Abbott, Kelvin Harrison Jr. Directed by Trey Edward Shults. Rated R. Opens Friday citywide.

Something went very wrong with the outside world at some point before It Comes at Night begins, but neither the characters nor the audience know what that is. Holed up in an isolated house in the woods, Paul (Joel Edgerton), his wife Sarah (Carmen Ejogo) and their teenage son Travis (Kelvin Harrison Jr.) know only that they need to do whatever it takes to survive, and that they can’t trust anyone outside the family. Those ideas come into conflict when a stranger named Will (Christopher Abbott) shows up on their property, asking for help for his own family. Reluctantly, Paul allows Will, his wife Kim (Riley Keough) and their young son Andrew (Griffin Robert Faulkner) to move in, pooling their resources and fortifying their home against potential outside threats.

What has caused the mysterious illness that seems to have wiped out most of the population? Are Will and his family telling the truth about their intentions and their history? What is left of the world beyond the woods? And what, exactly, comes at night? The movie answers none of these questions, at least not directly, but writer-director Trey Edward Shults (Krisha) builds an effective atmosphere of mistrust and dread, with even the slightest hint of deception eating away at the fragile alliance among the characters. Framing much of the story from Travis’ perspective, Shults plays with perceptions, and by the end it’s not quite clear what’s real and what might be a fever dream. Some of that unease takes a little too long to build, and the lack of clear details about the world can be frustrating. But it’s frustrating—and terrifying—for the characters as well, and Shults puts the audience right alongside them, fumbling in the darkness of an uncaring world that offers no explanations or comfort.