Sometimes a movie benefits from a willingness not to be specific about something that, on its face, seems of paramount importance.
Director Trey Edward Shults (Krisha) bravely refuses to define the threat that endangers his characters in It Comes at Night. That bit of restraint determines almost everything else about his movie -- both in terms of its strengths and weaknesses.
All we know is that something unseen and mysterious has caused people to contract a highly contagious disease that inflicts terrible suffering and always proves fatal.
Faced with this mass contagion, Dad (Joel Edgerton), Mom (Carmen Ejogo) and their 17-year-old son Travis (Kelvin Harrison Jr.) have withdrawn to an isolated cabin in a woods. They've sealed their home which features a corridor leading to a red door, the only way in or out.
Set in the midst of what appears to be an end-of-the-world scenario, It Comes at Night makes wise use of its limitations, focusing on how people respond to a situation that's fraught with fear and peril.
The family does its best to protect itself from danger. When family members leave their cabin, gas masks give them an ominous, alien look. Inside, they try to keep their environment as impenetrable as possible.
Early on, the family confronts an intruder (Christopher Abbott). As it turns out, Abbott's character also has a family. He offers to share food in return for shelter and water. After plenty of initial doubts, Edgerton's Paul agrees to join forces with a new family, which also includes a wife (Riley Keough) and a child (Griffin Robert Faulkner). None of them has yet to contract the sickness.
Harrison gives the film's best performance, ably reflecting the disoriented quality that accompanies what seems to have been the family's sudden retreat from everyday life, as well as the gloomy acknowledgment that the future must be bleak.
It doesn't help that Travis also is haunted by what he sees in the movie's opening scene, the mercy killing of the family's grandfather (David Pendelton), an early victim of the unidentified "sickness," a malady that causes those who suffer to breathe unevenly and break out in festering sores.
For all its virtues, It Comes at Night also makes us realize that this kind of concentrated, hot-house approach to filmmaking can hamper the way characters are deepened or a film's themes are enriched.
Still, most of the performances click. Behind a thick beard, Edgerton does pared-down work in his second interracial relationship movie since Loving, and Abbott conveys an understanding of the harrowing difficulties involved in negotiating an impossible situation. The script shortchanges Ejogo, as well as any potential racial issues.
If there's real horror here, it has less to do with jolts and gore than with the realization that under extreme conditions, mistrust can become an essential, if double-edged, survival tool. That's a truly scary idea -- and one that seems to fit the precarious moment in which we currently find ourselves.