You Might Be the Killer is a 2018 American supernatural slasher film directed by Brett Simmons and written by Covis Berzoyne, Thomas P. Vitale, and Simmons, based on an idea by Chuck Wendig and Sam Sykes. The film stars Fran Kranz and Alyson Hannigan, and features Brittany S. Hall, Patrick Reginald Walker, Keith David, and Bryan Price in supporting roles.

At Camp Clear Vista, panicked lead counselor Sam hides in a cabin and calls his friend Chuck, a horror movie enthusiast, and explains that a masked murderer is roaming the campgrounds. Asked for more details, Sam begins recounting his first day at the camp with fellow counselors and several friends, including his ex-girlfriend Imani.

While on the phone with Chuck, Sam momentarily blacks out and wakes up to the cabin on fire. Sam escapes, briefly spotting the masked killer, and finds a new hiding spot. With Chuck's help, Sam recalls more events.

After discovering several dead bodies, the group found themselves trapped at the camp. While patrolling the woods for the killer, Sam stumbled upon Freddie and Nancy, who for some reason could not hear him. As he witnessed the killer slaughtering them, Sam suffered a blackout.

As Sam is covered in blood, has the killer's weapon as well as a mysterious wooden mask, Sam and Chuck conclude that Sam may be the killer. His blackouts were moments where the "killer" personality took over. After Sam makes several unsuccessful attempts to destroy the mask, Chuck theorizes that the mask may have imprinted on him. Fearful that the surviving counselors are going to kill him, Sam goes back into hiding. Chuck asks Sam to remember how everything started.

After flashing back to several kills, Sam recalls telling the story of the mask's origin, which happened right at the campground many years ago. The origin of the mask dated back to the early day of colonization of European settlers when a group of Cajun people migrated to the land, bringing their dark magic with them. The Cajun black magic went awry and unleashed a dark entity that possessed people and made them massacre each other until a powerful sorcerer sealed the entity in an oak tree. Centuries later, a woodcarver crafted a mask from a tree containing a dark spirit. Influenced by the mask, the carver murdered many people until he himself was killed by a young woman. He was buried along with the mask. The bored group start to look for the grave.

One of his friends, Drew, tricked Sam into revealing the woodcarver's grave. Drew uncovered the mask and, when warned not to wear it, put it on Sam as a joke. A possessed Sam recovered the woodcarver's weapon and killed Drew.

Sam recalls more murders, concluding with the last kill involving throwing Imani into a spike pit. Sam's feelings for Imani allows him to take off the mask. Keeping track of the kills, Chuck advises Sam to be aware of Jamie, who might be the Final Girl.