I Know What You Did Last Summer (Lois Duncan, 2011)

It was only an accident but it would change their lives forever. Last summer, four terrified friends made a desperate pact to conceal a shocking secret. But now, someone has learned the truth, and the horror is starting again. There is an unknown avenger out there who is stalking them in a deadly game. Will he stop at terror—or is he out for revenge? This summer, four friends are going to learn that some secrets just won't stay buried.