In 1914, the luckiest man in town Tommy Murphy is overjoyed when the girl of his dreams, Caitlin O'Leary, agrees to dance with him in the town festival despite all rumors that she is a witch. The event is ruined when a young woman named Violet surprises him by showing her feelings for Tommy by kissing him in front of his date. Tommy tries to keep Caitlin from running off, only for him to accidentally tear her dress and humiliate her by revealing her underwear. This proves to be too much for Caitlin to take, and being a witch, she curses Tommy and all of his descendants with incredibly bad luck. He tries to find her so they could reconcile and reverse the curse, but is heartbroken when he learns that she married someone else. One hundred years later, his great-great-granddaughter Meg Murphy is desperate to end the family's curse. Together with her brother Charlie, Meg finds Tommy's diary and finds out that to get rid of the curse she needs to give Tommy's "lucky coin" to a descendant of Caitlin. They successfully manage to steal their great-great-grandfather Tommy's lucky coin from the Harvest Hills Historical Museum. Afterward, Meg realizes that Ivy Murray, a mean girl at school that picks on her, is a descendant of the O'Leary family and decides to give her the coin; her crush, Brett, asks her to the festival and she realizes that he's a descendant of Caitlin as well. At the dance she gives him the lucky coin, hoping to break her curse; however, a piece of Tommy's diary winds up in Charlie's hands and reading it, Charlie realizes the coin just ends up transferring the curse to Brett's family. Meg is horrified when she discovers what has happened and arrives at his house to witness his house getting ransacked by an angry monkey. Ivy answers the door, and upon learning that the bad luck came from Meg giving Brett the coin, she grows angry. Meg manages to convince Ivy that she never intended for this to happen and Ivy realizes she's always been mean to Meg since her cursed accidents affected her as well but realizes that it's not Meg's fault. The two race to the closing ceremony, where Brett gives Meg the coin back. She then almost falls off a flag tower but is saved by Brett, who then kisses her. Afterwards, Meg and Ivy become best friends and she and Brett are dating. Meg goes to science camp after all and accidentally invents a potion that grows hair on bald heads. Meg realizes that her curse is what makes her special. She puts back Tommy's diary with the coin after reading in the last part that Tommy, due to his bad luck, meets his beautiful wife at the hospital and throws his coin into the fountain causing a flood. Even so, he believes that it's the attitude that counts. Meg and her family go on vacation to visit the Grand Canyon and end up causing more bad luck, with Ivy and Brett running for their lives, but laughing about it.
