An ancient monster emerges from a cave and starts killing people. It's man-sized and covered in a thick armor-like skin impervious to all conventional human weapons. A reporter follows the monster through its killing spree. It appears to eat humans. The reporter follows the beast back to its cave and dives in after it deep into the earth. He finds an elaborate underground structure of passages and halls littered with skeletons of humans, as well as seemingly dead monsters of the same type as the one who just went on a killing spree.
The reporter finds the living monster seemingly in hibernation in a hall. He finds a boy resting with the monster. The reporter tries to quietly get the kid away from the monster but the kid wakes and screams and bites the man. The monster stirs but is lethargic and only makes a halfhearted attempt to chase after the reporter who escapes to the surface.
The reporter writes up an article with documentation in the form of video and photos taken with his smart phone. The cave area is cordoned off and the military engages in some operations around there, presumably in the caves. The child is not identified even though his picture is in the media--one of the photos the journalist took was of the kid's face.
A folklorist from the local university emails the reporter and tells him the Native Americans in the area had stories of a rock monsters that kidnapped babies and used them as lures and as watchmen and guardians to protect the monsters while the monsters slept. The boy would have been kidnapped locally around eight to ten years ago, probably as a baby.
The reporter scours records and finds that such a boy fits the profile--kidnapped from a family outing in the woods near the caves. The journalist contacts the mother and they go to the cordon set up by the military and tell the guard there about the possibility the mother's child was kidnapped. The guard at the cordon arranges a meeting with a general, who explains that special forces were able to rescue a child, but were not able to find the monster.
The mother goes to the hospital where the child is. The kid is unruly and is restrained in his hospital room. The mother and the reporter look in on the kid through a window and are disturbed by his screaming and thrashing. The lights go out in the hospital, gun fire is heard, and the lumbering figure of the monster is seen. The monster makes its way to the room where the kid is, smashes open the wall and rescues the child from his restraints. The monster and child make their way in darkness towards the exit. The reporter and mother shadow the monster.
A policeman roaming the corridors of the hospital runs into the monster and pulls his gun. He fires in the darkness as the monster's shadowy figure. The mother and reporter yell at him to stop as the child is with the monster. The monster drops to his knees and is motionless. The gunfire ceases. The lights flicker on and the monster remains frozen, on its knees, holding the boy in his arms. The boy is dead from a gunshot.
The mother and reporter and officer approach the monster but it doesn't move. The police and military swarm the hospital. The monster never moves again, apparently dying from some unknown cause, as no bullet pierced its armor-like skin. Its body is taken by the military. Later, the mother is asked if she wishes to do a DNA test to see if she is the boy's mother, and she declines.