Directed by Joel Schumacher, the film stars Jason Patric, Corey Haim, and Kiefer Sutherland, and co-stars Jami Gertz, Corey Feldman, Dianne Wiest, Edward Herrmann, Alex Winter, Jamison Newlander, and Barnard Hughes.

The title is a reference to the Lost Boys in J. M. Barrie’s stories about Peter Pan and Neverland.

After a strange and mysterious murder at fairground at the immediate start of the film, Michael and Sam move with their mother Lucy to Santa Carla, a coastal California town plagued with gang activity and unexplained disappearances. The family moves in with Lucy’s father, a cantankerous old man who lives in the outlying suburbs of town and who decorates his house with the product of his hobby: taxidermy.

The center of town life seems to be the local boardwalk. While Lucy gets a job at a local video and electronics store run by a man named Max, Michael is fascinated by a beautiful young woman who he sees at an outdoor concert. After following her along the boardwalk, he sees her getting on a motorcycle with David, the leader of the local gang. The following night he finds the young woman again and learns her name is Star. As they are about to leave together on Michael’s motorcycle, David reappears and provokes Michael into following him and his cadre. They drive to some sea-cliffs where Michael is almost baited into going over the edge. Michael punches David, who merely sees potential in Michael and invites him to the gang’s lair, an old dilapidated hotel that sank beneath the ground.

At the hotel, the gang leads Michael through an unsettling initiation involving Chinese takeout. At the end, an annoyed Michael takes a swig from a bottle which contains a dark unknown liquid (which turns out to be vampire blood). The gang then takes Michael out to where some railroad tracks cross a foggy gorge; one by one the group jumps off the tracks and out of sight. Michael realizes they are hanging from exposed reinforcement bars. They talk him into joining them under the tracks. As the train roars overhead, the reinforcement bar shakes and one by one the members of the gang fall into the foggy gorge, but they do not die; Michael can hear them goading him to fall. Unable to lift himself up, or hold on any longer, Michael falls in as well.

Michael wakes up in his bed still in the clothes he wore the night before. He is groggy and disorientated. It’s mid-day and he has no clue how he got there. In the meantime, Sam has made the acquaintance of two young brothers, Edgar and Alan Frog. The Frog brothers run the local comic book store for their burn-out parents. Upon learning that Sam is new to the area they force a couple of vampire themed comic books on him despite his protestation that he doesn’t like horror comics. They explain to him that they may one day save his life. Sam is initially mocking of their claims but becomes suspicious of Michael’s increasingly bizarre behavior, including sleeping all day and being sensitive to sunlight. One day, as Sam is taking a bath, Michael, driven by bloodlust attempts to attack him, but is fought off by the family’s dog. Afterwards Sam becomes convinced that Michael is a vampire when Michael begins uncontrollably floating around the house. In a panic he calls the Frog brothers, who inform him that he must kill Michael, but Sam refuses to murder his brother. Michael returns to the gang, and they reveal that they are indeed vampires and murder a group of teenagers at a bonfire party. David explains that Michael must feed in order to survive, but Michael refuses to kill and leaves. Returning to the groups lair he discovers Star, who reveals their nature as “half vampires” who will not achieve full vampire status until they have killed. She says that David had intended for Michael to be her first kill but that she cannot do it. The two make love.

Sam has discovered, from comic books that if the “head vampire” is killed then all of his subordinate vampires will revert to human form. Unwilling to kill his brother he enlists the Frog brother’s help in trying to kill the head vampire. This proves difficult, as it is not immediately evident who this is. Sam and the Frog Brothers suspect Max, who has begun dating Sam’s mother and who they have never seen during the day, but their tests during his visit to their house all indicate he is human.

The teens determine that one of the gang must be the head vampire. Michael, disgusted at the transformation he has undergone, joins them in an attempt to rescue Star and her young brother Laddie, also a “half vampire” and reverse their condition. The group travels to the gang’s lair and while Michael rescues Star and Laddie, the Frog Brothers and Sam travel deep into the lair to kill the vampires. They discover the gang asleep, hanging from the roof like bats. Unsure of which one of the gang is the head vampire the Frog brothers stake Marko, one of the gang members who expires in an explosive fashion. With the rest of the gang woken by the commotion the three boys retreat, with Sam narrowly escaping capture by David. That night, while Lucy is on a date with Max and their grandfather is away, the teens barricade their house and prepare for the gang’s assault. Among other things they steal holy water from a church and fill squirt guns with it to use against the vampires. That night the gang attacks. With the help of Sam’s dog, Nanook, the defenders pick off the gang-members one by one, with Sam shooting Dwayne through the heart with an arrow, Nanook knocking Paul into a bathtub full of holy water and garlic, and Michael impaling David on some deer antlers in his grandfather’s taxidermy workshop. However, Michael is still a vampire, and Max and Lucy then appear and Max reveals himself to be the head vampire after all; the tests hadn’t worked because he had been freely invited into the house. He reveals that he had wanted Lucy as his mate and that his “family” and hers would merge. Lucy is horrified, but Max threatens to kill Sam unless she joins him. As Max is about to bite Lucy’s neck, her father crashes his jeep through the wall of the house; the vehicle’s hood is piled up with large fence posts, and one of them impales Max, killing him. These fence posts had earlier, inexplicably, been put into the ground by Grandpa with the spiky end up. As the others stare in amazement, Grandpa casually gets a root beer from the refrigerator and remarks, “One thing about living in Santa Carla I never could stomach… all the damn vampires.”