I Know What You Did Last Summer is a 1997 horror film. It stars Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe, Freddie Prinze, Jr., and Anne Heche. The screenplay was written by Kevin Williamson, which was based on a popular novel by Lois Duncan. The film was followed with the sequels, I Still Know What You Did Last Summer and I'll Always Know What You Did Last Summer.