Phil Burbank (Benedict Cumberbatch) is a rancher with a cruel tongue. When his crew of cowboys goes for a bite to eat in town one day, he's served by widowed Rose (Kirsten Dunst) and her teenage son Peter (Kodi Smit-McPhee), but Phil's constant nasty comments upset them. Phil's brother George (Jesse Plemons) comforts Rose and takes a shine to her. He soon marries Rose and brings her and Peter home to live with him and Phil on the ranch.
Phil's attention towards the two takes a curious turn. Phil continues to torment Rose with veiled comments and by whistling a tune that haunts her, but he also takes Peter under his wing, teaching him to ride. Whether this means Phil's attitude towards them is beginning to soften, or whether he's cooking up something more sinister remains to be seen.