In the tradition of Italian horror from the 1960s, Sibling Rivalry is a dark tale of secrets, lies and masked killers run amok, while still retaining a sense of humor. Camille, 15, and her sister Ariana, 12, return to their secluded summer home on the isle of Victoria, where a year earlier, their mother committed suicide. Their father, James Stockman, producer of a popular TV series Memoirs of a Teenage Necromancer, insists that the trip is good therapy for them all. Shortly after arriving, Stockman is called back to Los Angles on `business` leaving the girls home alone. In defiance, the girls throw a party with some local teens. That`s when the fun begins. As the body count rises, multiple masked killers surface, and terrifying family secrets are revealed.