"I Know What You Did Last Summer" is a 1997 American slasher film directed by Jim Gillespie. The movie is based on the 1973 novel of the same name by Lois Duncan. It stars Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe, and Freddie Prinze Jr. The plot revolves around a group of teenagers who accidentally kill a man while driving and decide to cover it up. One year later, they begin receiving threatening messages from someone who knows their secret, leading to a series of suspenseful and deadly events. The film was popular in the late 1990s and helped launch the careers of its young stars. It also sparked sequels and is considered a classic of the teen horror/slasher genre. If you'd like, I can provide more details about the plot, cast, production, or reception.