The latest installment in the "I Know What You Did Last Summer" horror franchise which focuses on a seemingly harmless Fourth of July prank that ends in the unexpected death of a friend of four teens from Broken Ridge, Colorado. The friends make a pact to keep the death a secret from the authorities, despite one's desperate protest. Over the course of the following year, the four teens find their friendships horribly strained from keeping the secret. As the next Fourth of July approaches, the four teens all find themselves being victimized by a mysterious menace. The friends try to survive and figure out the identity of their tormentor before they end up dead themselves.