Susanne Bier's film adapts Josh Malerman's first novel, keeping its premise exactly: something outside drives anyone who looks at it to suicide, so survival means moving blindfolded. The novel's structure survives too. It cuts between a house full of strangers in the first days and a river journey years later with two children, and the film keeps that braid, which is what lets it withhold what happened in the house until the river has made the stakes clear.