The story follows a brother and sister, Darry (Justin Long) and Trish Jenner (Gina Philips), who are on a road trip through the countryside. Their peaceful drive is disrupted when they encounter a mysterious truck that aggressively tailgates them. Later, they witness the driver dumping what appears to be a body wrapped in a bloody sheet into a drainage pipe near an abandoned church.

Disturbed and curious, they return to investigate, leading to the discovery of a horrifying underground lair filled with dead bodies sewn together on the walls and ceiling.

Soon, they find themselves being hunted by a terrifying creature, known only as The Creeper — a demonic being that awakens every 23rd spring for 23 days to feed on human body parts, which it uses to regenerate its own.