Branded as a 'nerd' and harassed by the school bully, 12-year-old Arthur is rescued by a magical troll who knows that the boy unwittingly holds the secret to defeat an evil dragon. Arthur's loving mom, struggling to keep her devious ex-husband from gaining custody of Arthur, dismisses her son's 'fantasies' until she realizes the all-too-real immediate danger. She joins forces with Arthur, the troll, and a dashing but washed up video-game master. Together, they hope to conquer the dragon and the wicked vice-principal who threaten civilization.