Marta, a middle-aged mother, is searching through the woods for her thirteen-year-old son Teddy. Teddy does not have friends and is different from other children, but he asked her for a birthday party this year. However, Teddy had seemed distracted during the party, and kept looking to the parking lot like he was waiting for someone. The party had ended poorly, and now she is searching the woods, while her boyfriend Doug and his daughter Emmeline wait back at the park where the party took place. Marta feels a hand drag her down from where she is climbing, and then she hears footsteps approaching that are too heavy to be Teddy's.
Nothing about the party had gone as Teddy planned either. He had found a man online named Mr. Forble who advertised that he would deliver trouble and havoc; however, the man had not shown up to the party as promised. Angry, Teddy had punched his mother in the face and ran away into the woods. Teddy hears Marta calling for him, and he resists the urge to run to her for comfort. He hears an engine backfiring in the distance, and knows that Mr. Forble has arrived.
Micheal, one of Teddy's classmates who attended the party, sits in the front of his mother's car while she talks on the phone outside. Teddy scares him, and some of his friends tease Teddy. At the party, Micheal ran into Teddy in the bathroom. Teddy showed him a video of someone sitting in a chair, begging to be let go. The ending of the video almost causes Micheal to pass out. Teddy tells Micheal that he likes him, and to tell his mother that he wants to leave early. Micheal's mother does not allow this, but nothing ends up happening during the party. In the car, Micheal sees a truck pull up next to him. He sees a tall man get out, and avoids looking towards him. The man goes up to Micheal's window and says "Hello, little guy. I'm late." 
Emmeline, the daughter of Marta's boyfriend, is a freshman in college. Her roommate, Flo, is odd, and sits inside all day commenting on Youtube, Instagram, and Reddit. Emmeline's father and Marta broke up shortly after Teddy's disappearance. Emmeline comes back to her room crying after a cast party one day. Flo attempts to cheer her up, and shows her videos on Youtube. She asks if Emmeline has heard of Mr. Forble, who Emmeline believes is an internet hoax. Flo pulls up Mr. Forble's videos, and says he is all about vengeance. In one video, someone is getting chased through a field, and the laughter sounds familiar to Emmeline. Flo says that Mr. Forble always comes, but there is always a catch. They watch another video, where a boy sits with his hands bound in a chair. Emmeline recognizes the boy as Teddy. Something horrible happens in the video, and Emmeline asks Flo to play it again.