There’s a specific sub-genre of horror movies, the “siege” type scenario, the kind of movie where people are essentially locked into one area, one house or one cabin (or in the case of Dawn of the Dead, a mall), and they are unable to leave because the world around them is crumbling and rife with threat. In the case of It Comes at Night, there is a deadly, highly-communicable disease. Contact with the disease is, as of now, pretty much 100% lethal. In the vein of George A. Romero or John Carpenter, the disease isn’t the monster—the disease just does what a disease does—the real monster is humanity.
Something John Carpenter has said again and again is that it’s so easy to say that monsters are out there, that they live in the shadows, that they dwell in the darkness. But what’s really scary is the truth, that the monsters are already among us and we are them.