Cirque du Freak: The Vampire's Assistant is the 2009 film adaptation of the Vampire Blood trilogy of the book series The Saga of Darren Shan by author Darren Shan.
A teenager unknowingly breaks a 100-year-old truce between two warring factions of vampires; vampires who do not harm their victims and vampaneze who kill whomever they feed on. Darren Shan (Chris Massoglia) and his best friend, Steve Leonard (Josh Hutcherson), go to a traveling freak show and Steve recognizes one of the performers as a vampire. Steve goes to see the vampire, Larten Crepsley (John C. Reilly), after the show and after a small talk, Steve reveals he hates his life and subsequently tries to convince Crepsley to turn him into a vampire. Crepsley refuses, telling him he has bad blood, and Steve swears to kill the vampire and leaves, furious. Darren, who is hiding in the cupboard after stealing Crepsley's spider, overhears the whole thing. When Crepsley realizes that Madam Octa has been stolen, Darren runs away. Outside there is a limo waiting for him, which he is told to get into. Inside he meets Desmond Tiny (Michael Cerveris) and mad Vampaneze Murlough (Ray Stevenson). They drop him off at his house where he sneaks back into his room. The next day at school, Darren tries to take a look at Madam Octa, but Steve catches him and tries to get a close look at her while holding her cage. The bell rings, startling Steve and making him drop the cage, and she escapes. As Madam Octa tries to escape the school she creates chaos and Steve chases her, trying to kill her, and Darren follows after trying to save her. At the last moment Madam Octa slips into Steve's shirt and bites him and makes good her escape. Darren then goes to Crepsley to ask for the antidote and is offered a deal by him. Crepsley will keep Darren safe from Mr. Tiny and only give him the antidote if Darren becomes a vampire's assistant for him which will make him a half-vampire. They administer the antidote to Steve, after which Darren sounds the hospital alarm, forcing Crepsley to leave without him. Darren nearly hurts his sister due to the blood lust within him and agrees to leave with Crepsley in order to spare his family, and to go to the Cirque du Freak. He fakes his own death and a funeral is held for him. Steve notices the scars on Darren's fingers and realizes he has become a vampire. When Crepsley digs up Darren's grave they are attacked by Murlough, who tries to kidnap Darren and make him into a vampaneze. They lose Murlough and return to the Cirque. Darren meets the snake boy, Evra Von (Patrick Fugit), and Rebecca (Jessica Carlson), the monkey girl. Meanwhile, Steve is contemplating suicide. Mr. Tiny stops him and offers him a chance to become a Vampaneze, like Murlough. Tiny learns Darren has not fed on humans yet and sends Vampaneze after him, knowing that he will be weak. Darren escapes, so they kidnap Rebecca and have Evra tell Darren "to go home". Meanwhile Mr. Tiny makes contact with Steve and entices him to join his vampaneze by playing on his resentments and insecurities. After an initiation, and being inducted into the evil group, Steve has Murlough capture Darren's family. Darren arrives home to find his family missing and a flier for Cirque du Freak. Darren arrives at the theater, where Murlough and Steve are waiting for him. They fight, but Darren is weak from not feeding. Crepsley arrives to fight Murlough. Rebecca frees herself, while Mr. Tiny watches from the balcony. Rebecca offers Darren some of her blood. He eventually agrees and fights with Steve using his new powers. Crepsley stabs Murlough and with his dying words announces that the truce between the two clans is broken. Steve and Darren fight. Tiny stops them and then turns Murlough into a Little Person. Tiny and Steve then leave. Left by themselves, Rebecca and Darren then share a long heartfelt kiss before being interrupted by Mr. Crepsley. When they all return to the Cirque du Freak, Darren is voted in by the Cirque's members to stay. Later, Gavner Purl (William Defoe) comes to inform Crepsley that they must travel to Vampire Mountain tomorrow morning. Darren and Evra return to their tent to find out that Darren now has a new coffin with speakers installed in it, a present from Mr. Crepsley.