Brian is a twelve year old boy. His parents have signed him up for a day camp at Thunder Lake. There used to be rumors circulating that there used to be werewolves at the camp. The Thunder Lake camp is meant for teenagers, so Brian and another kid named Kevin were the youngest campers. Kevin is a nerdy red haired boy who is always picked on by the three fifteen year old bullies: Jake, Phil, and Don.
Brian is paranoid; he is certain that there are werewolves at this camp. One time, while Don is smiling, Brian thinks that he sees fangs. At night, Brian sees Phil running through the woods like a wild animal. Several nights later, Brian witnesses Jake howling at the moon. Brian runs off to warn Kevin that Jake, Phil, and Don are werewolves. However, when Brian finds Kevin, he sees Kevin eating a piece of raw hamburger meat.
Brian knows that there is a full moon coming, and he is terrified. He tries to get his parents to take him out of camp, but they won't. Brian is forced to spend a night in the woods with four potential werewolves during a full moon.
The night of the full moon finally arrives. Brian peeks out of his tent to see what the other campers are doing and sees them turning into werewolves. Brian's terror is soon stopped when the "werewolves" take off their masks. The costumes were all a part of a big initiation joke. The other kids are all laughing when Brian begins to feel something strange, thick hair quickly spreads all over his body, he starts to grow fangs and claws and he transforms into a werewolf. Brian realizes that this camp might be fun after all. He then begins chase some other campers that arrive.