I Know What You Did Last Summer is a 1997 American slasher film based on the 1973 novel of the same name by Lois Duncan. The film changes many aspects of the book, which was not a slasher novel. The film also draws inspiration from the urban legend known as The Hook.The film stars Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe and Freddie Prinze Jr., with Anne Heche and Bridgette Wilson appearing in supporting roles.