In a post-apocalyptic world, an unspecified, unseen evil threatens the few remaining humans, generating among them the realization that they must work together, but also intense paranoia and distrust. One man (Joel Edgerton) who has built a secure, self-sustaining home for his family is severely tested when he reluctantly takes in a second desperate family. Part of this film’s head-screwing terror stems from its nearly unbearable uncertainty. It plants questions (What is “it”?), but then refuses to answer them. The other part is its sheer plausibility. The director is Trey Edward Schults (Krisha). (91 min)