Chris Emerson, a young disgraced former surfing pro, and his younger sister Nicole move to Luna Bay to live in a house owned by their Aunt Jillian following the death of their parents. Chris leaves his address at the home of Edgar Frog, the town's surfboard shaper, in hopes of getting a job. Chris is approached at their new home by former pro surfer Shane Powers, who invites him to a party that night.
Chris and Nicole go to the party, where Shane and his tribe are entertaining themselves with the human guests. Chris showers with a sexy girl named Lisa, and Shane gets Nicole alone, chats with her for a bit, and then tricks her into drinking his blood. When Chris learns that Nicole has been with Shane, he angrily, and protectively, takes her home, where she begins to manifest vampiric strength and rage. But before she hurts Chris, she is knocked out by Edgar, who reveals that he is a vampire hunter, and Nicole has been infected with vampirism. Chris throws Edgar out of the house. Then, Lisa shows up and pretends to chat with Chris for a bit before she finally tries to seduce and feed on him. In fending her off, he accidentally impales her on a mounted rack of antlers, killing her explosively.
Finally, convinced of the situation, remembering what Edgar said and believing that he was right, Chris seeks out Edgar's help. Edgar explains that Nicole is only half-vampire, and will remain that way unless she feeds, and she can be turned human again if they kill the head vampire before that. Chris interrupts her just before she can feed on Evan, a nice guy who has been courting her, and explains what is happening to her, and Nicole is surprised at what she almost did (because she believes herself to be a vegetarian). However, Shane draws her to their lair.
Chris and Edgar - who lost an unnamed sibling to the vampires - plot for Chris to "join" the tribe of vampires in order to learn the location of their lair. He drinks Shane's blood and begins to develop vampire traits, but when the tribe (minus Shane and Nicole) feed on a group of girls, he refuses, and kills one of the vampires in self-defense. Edgar joins him and they go to the lair, killing the tribe members one at a time.
Meanwhile, Shane goads Nicole to kill Evan, whom they have bound and gagged for her, but she refuses. With Chris' help, she kills Shane, returning them both to normal. They thank Edgar, who promises to bill them for his services, and Evan takes the opportunity to ask Nicole for a date. At home, they are confronted by their aunt, who believes they have been doing drugs, and promises zero tolerance.
In a mid-credits scene, Edgar encounters Sam Emerson, now a vampire. They exchange some dialogue and charge at each other as the credits resume.
In one alternate ending, Edgar is cleaning up after the vampire hunt, when Sam Emerson (who is not a vampire) knocks on his door. Sam warns him that his brother Alan is coming to settle the score. Edgar is reluctant to accept Sam's help, but Sam insists he needs it. The scene ends with vampiric Alan and a female companion driving wildly to confront Edgar.
Another alternate ending is a slightly extended version of the first, but with Sam wearing black sunglasses and showing Edgar bite marks on his neck.
Hans Rodionoff originally wrote a script about surfing werewolves titled The Tribe which was turned down by studios including Warner Bros for its resemblance to The Lost Boys. Warner Bros studio executives changed their mind when they decided on a sequel, who then persuaded Rodionoff to alter the script as a sequel, including changing the werewolves of the original to vampires.