Is ‘I Know What You Did Last Summer’ Based On A True Story?

I Know What You Did Last Summer (1997) is an iconic 90s horror movie starring Jennifer Love Hewitt, Freddie Prinze Jr., Sarah Michelle Gellar and Ryan Phillippe.

The plot follows the group of four friends the summer after they graduate from high school. After spending the Fourth of July partying on a beach, they drive down a winding South Carolina road and accidentally hit a pedestrian. Worried about their futures if they go to the police, the friends decide to dump the body in the ocean and never speak of the night again. However, the following summer they start getting menacing notes saying “I know what you did last summer”, and are then hunted down by a hooded figure in a fisherman’s slicker who has a hook for a hand.

You might recall that I Know What You Did Last Summer is based on a 1973 young adult fiction book of the same name by author Lois Duncan. You might even remember that Duncan hated the adaptation and spoke out against violence in cinema when it was originally released. But did you know the reason for this was that Lois Duncan’s daughter, Kaitlyn Arquette, was murdered in 1989 and the case wasn’t solved until August of 2021?

In her own words, Lois Duncan grew up as a shy bookworm who sold her first short story at the age of 13. She was accepted to Duke but dropped out when she got married. After divorcing that husband in 1962 she supported herself by writing for greeting cards and pulp magazines before establishing herself and selling novels. Her first book Ransom was about a group of high school students being held hostage on a school bus. In 1973 she published I Know What You Did Last Summer, a fairly tame suspense novel not at all like the gory slasher movie.

Wes Craven directed a TV movie of Duncan’s novel Summer of Fear in 1978. Her 1978 novel Killing Mr. Griffin, considered controversial for the portrayal of students getting revenge against a teacher, was made into a TV movie starring Jay Thomas, Scott Bairstow, and Mario Lopez in the late 90s. Around that time Duncan sold the film rights to I Know What You Did Last Summer for $150,000, and no claim to any residuals.

When the violent adaptation appeared in theaters a few years later, Duncan had harshly criticized the film as “worse than bad. It’s totally sick.”

The gore was beyond belief. I write suspense and scary stuff, but I have never written gore in my entire life. I have never sensationalized violence. It’s always been a vehicle to show the pain that violence can cause. There’s so little connected to my book (in the movie) that I don’t know why they ever wanted it.

The reason Duncan responded so strongly to the sensationalized slasher movie version of her work is that between the writing of her horror/suspense works and the film adaptation, her daughter was murdered. She told the Chicago Sun-Times: “My daughter Kait was chased down, and her brains were blown out… So I’m particularly sensitive about desensitizing kids to violence and turning murder into a game.” Deeply traumatized by her daughter’s sudden death, Lois Duncan stopped writing horror and suspense novels. Her later works were children’s books and prose and poetry about losing her daughter.

Duncan’s daughter, Kaitlyn Arquette, was only 18 and a recent high school graduate when she was gunned down in her car on July 16, 1989 in Albuquerque, New Mexico. An unskilled police investigation labeled the murder “a random drive by” and left the case unsolved for over 30 years. A segment about the murder even appeared on Unsolved Mysteries during the height of the show’s popularity.

When police arrived at the scene, they found a man named Paul Apodaca standing by Kaitlyn’s car. He was never interviewed about that night. 31 years later Apodaca confessed to murdering Kaitlyn, he said his motive was “hatred for women”. He even admitted to reading Lois Duncan’s book, Who Killed My Daughter?: The Startling True Story of a Mother’s Search for Her Daughter’s Murderer. Sadly Lois Duncan died in 2016 and never saw justice for her daughter.

The production company who made the 1997 film said the fact that Duncan’s daughter had been murdered was “not well known” by the people who made the film. The source material, Duncan’s 1973 novel, was written over a decade before her daughter’s murder so there’s no way in which the film is based on Duncan’s daughter or any kind of true crime story. The ties to real life crimes in this case only highlight the anguish of a mother whose daughter’s murder investigation was egregiously botched by police, understandably giving her a distaste for violence, including later adaptations of her works.