1,000 years ago in Ireland, an evil Leprechaun celebrates his 1,000th birthday on St. Patrick's Day. He tells his slave, a man named William O'Day, that he has found the perfect bride. Once he marries, the Leprechaun promises to grant O'Day his freedom. O'Day is overjoyed at first, but is horrified to see the Leprechaun has chosen his beautiful daughter. Despite O'Day's pleas, the Leprechaun says that she will be his once she sneezes three consecutive times. Once the Leprechaun manipulates her to do so, O'Day says "God bless you, my child,", freeing her from the Leprechaun. O'Day is then killed by the Leprechaun, who promises to marry an O'Day descendant in a thousand years' time. On St. Patrick's Day in present-day Los Angeles, a young man named Cody works with his uncle Morty giving "dark side" tours, a scam that drives tourists to alleged resting places of celebrities. When Morty is too drunk to drive, Cody does so, forcing him to cancel a date with his girlfriend Bridget. He drops Bridget off at a go-kart track run by his pretentious rival Ian. Prior to Bridget's departure, the Leprechaun emerges from one of the tour stops: an Irish tree that was present at the home of Harry Houdini. The Leprechaun tears out the gold tooth of a homeless man and goes off to search for his new bride, revealed to be Bridget (a descendant of the O'Day bloodline). A frustrated Cody speeds through a red light and is arrested. Morty picks him up from the police station.