Twins Frankie and Tracy Considine are excited to be moving to Leams, Massachusetts to live in their grandmother's beautiful old house. With their mutual thirteenth birthday looming, Tracy and Frankie have much to look forward to...or so they believe.

When their beloved dog Muffin disappears, they begin to wonder if the move was so great after all. Tracy's friend, Carol, is distant, odd—but Carol did just turn unlucky thirteen, so she wonders if that's all there is to it. Tracy hears strange sounds coming from the woods that everyone insists is her imagination. Bizarre events begin to occur: Girlfriends turn up with frightening tattoos, a young boy abruptly disappears, and a fortune-teller warns Tracy to be wary of those she normally trusts. Eagerly looking forward to their thirteenth birthday party, she rationalizes away all her doubts while Frankie discovers the town's tragic curse and realizes he and his sister are in grave danger. Either he saves them from an event that's destined to happen, or they'll be the next victims!