Carefree and desperate to avoid any responsibility, Jessica, a college student, visits a yard sale to buy a gift for her best friend. However, the music box she brings home is haunted by a vicious demonic entity eager to feed off the lives of all who hear the box's melody. After her best friend takes her own life, Jessica seeks the aid of two ghost hunters, but they too find themselves out of their depth. Desperate to free herself of the cursed box, she searches for the box's origin only to find that true evil begins with best of intentions.

Fiercely protective single-mom Meredith Hendricks happens to also be the best cop in her quiet town on Lake Tahoe. When a black-market exotic species dealer named Clint, is paroled from prison, something he let loose begins to make its presence known. Swimmers and land-lovers alike begin to become part of the food chain at an unbelievable rate. Meredith and the new man in her life, a biologist named Peter, begin to investigate these brutal attacks and discover that they're not just hunting one eating machine, but a whole family of them. After a documentary crew is devoured when they don't take the threat seriously, it's up to Meredith, Peter, and the unlikely hero, Clint, to stop the most dangerous thing on the planet: A mother protecting its young. Not everyone will make it out alive, but those who do will never forget this summer at Shark Lake.