Outer Dark.

In Appalachia during the Great Depression, a young woman bears her brother’s baby. Her brother leaves the nameless infant in the woods to die, but tells his sister that the newborn died of natural causes and had to be buried. The sister discovers this lie and sets out to find the baby for herself. But as both brother and sister separately move through the countryside, three terrifying strangers are on their tails, wreaking death and destruction wherever they appear.