A film adaptation of a short story, written by Stephen King, that was originally featured in a March 1973 issue of Cavalier magazine & later in Night Shift, a collection of short stories all written by King.
Was originally meant to be released straight-to-streaming on Hulu, but the strong reception from test screenings prompted 20th Century Studios to instead give it a wide theatrical release.
The scene where Sawyer, played by Vivien Lyra Blair, wets her pants in fear after the light-show therapy in Dr. Wallace's office, is a direct nod to the Stephen King short story, when Lester Billings wets himself after seeing The Boogeyman right at the end of the tale.
Some scenes were so intense that they had to be changed after test screening. The audience screamed so loud that important dialog after the scene was lost. The editing was changed to put in pauses so the dialog could be heard.