Happy Death Day is the newest horror film to hit theaters and it’s looking to invigorate the teen slasher genre. While the concept itself is fairly straightforward, there are enough twists and turns that it’s easy to miss some of the clues that are laced throughout the film. The basic premise of Happy Death Day is that a young college student named Tree Gelbman is being hunted down by a ruthless, masked killer. However, the main concept in this movie is every time she dies Tree’s day will restart, allowing her another chance at deducing who is trying to murder her.
Unlike other time-based films like Edge of Tomorrow, Tree actually sustains damage after each reset. Her body progressively becomes weaker after each death, which means that at some point she will be murdered and will die when her day resets. Racing against time, Tree is forced to not only confront her own personal issues but find out who is trying to kill her and stop them.
(Warning Spoilers Ahead
When the third act kicks in Tree has already been killed around 15 times by her mysterious killer who is sporting a black hoodie, pants, and a baby mask (which is the college mascot). Waking up in Carter’s dorm room again after another unsuccessful night, Tree attempts to leave only to pass out at the door. She awakens in the hospital where she learns from a professor/doctor – who she is having an affair with – that her body is sustaining injuries that should have killed her. The doctor strongly advises she stays overnight, however, Tree realizes this will make her vulnerable.
Once she is alone, the student attempts to escape from the hospital and runs into the doctor’s office in search of his keys. After finding them, Tree discovers a baby mask in his desk and instantly suspects that he’s the killer. Confronting the professor in the hallway, the doctor is revealed to be innocent as he’s killed in front of Tree. A chase ensues that ends with the killer dropping a birthday candle into a pool of gases that causes a car Tree is locked in to explode.
After waking up again, Tree is almost pushed to her breaking point and decides to go out for dinner with Carter. At the diner, Tree reveals that both she and her mother share a birthday, however, her mom passed away a few years ago. This has made Tree’s relationship with her father difficult to the point where the two almost never talk. The duo is then interrupted when it’s revealed that a serial killer named Joseph Tombs was admitted to the hospital that is on Tree’s campus. Realizing that this could be the killer she rushes over only to discover he is free and has murdered the guard on duty. She’s soon discovered by the killer and is chased through the hospital, trapping her by the elevators.
However, right before she is killed Carter arrives and tackles the serial killer to the ground. A struggle ensues that ends with Carter being killed via a neck snap. Terrified, Tree runs away from Tombs and leads him into the hospital’s bell tower. Striking Joesph with a crowbar, the killer falls to the ground and for a brief moment, Tree has a chance to kill him and end the madness. She hesitates and realizes that killing Tombs would result in Carter staying dead so she goes up to the tower and hangs herself.
Reset once again, Tree spends her entire day making amends with all of the people she has wronged in her life. As night falls, Tree sets her watch timer to go off when there is a brief power failure that has happened at the same time on this day. Rushing off to the hospital, Tree tells the guard to go get help and enters the room armed with a pistol she took off the cop. Pointing the handgun at Tombs she attempts to fire only to realize that the safety is on. The killer takes this window of opportunity and attacks Tree, almost beating her into submission. Right before he can deliver the final blow, Tree’s watch goes off right as the power fails.
Plunging the duo into complete darkness, Tree grabs the gun and shoots Tombs when the lights come back on. With the killer defeated she heads back to her place and has her birthday cupcake with Carter to celebrate. Unfortunately for our hero, the day resets again which confuses Tree because she killed her murderer. Panicking, she rushes to her sorority home, goes to her room, and begins to pack her things in an attempt to flee this nightmare. Her roommate Lori offers her a cupcake like she has every single time before, however, this causes Tree to have a flashback.
Realizing that she hasn’t actually investigated Lori during her hunt for the killer, Tree remembers that the only time she had the cupcake was after Tombs was killed. This leads her to believe that her roommate poisoned the cupcake in an attempt to kill her. However, since Tree never ate it Lori had to improvise and used her credentials as a nurse to break into Tombs room, free him, and leave an outfit for the serial killer.
It’s then revealed that Tombs has never killed Tree outside of their one encounter in the hospital where she ended up hanging herself. Instead, Lori simply freed the killer and gave him the same outfit she wore when she murdered Tree over and over again. This would cause Tombs to take the blame for Tree’s death and Lori to escape without any issues.
When confronted about this, Tree tells Lori to eat the cake or she will go to cops. When her roommate refuses, she locks the door and a fight breaks out. Lori finally reveals that it was her that was trying to kill her this whole time. This scuffle with Lori being thrown out the window where she falls to her death ending the cycle. Since Tombs can never be freed by Lori in the hospital, Tree has nothing to worry about anymore. Relieved, Tree spends the night with Carter who decides to play a prank on her and makes her believe that the day reset again. To Tree’s relief, this is only a joke and she can finally move on with her life.
Interestingly enough Happy Death Day hints that the killer is Lori several times throughout the movie, but the most damning is during the first hospital chase scene. While the scene plays out to make the viewer believe that Tombs was chasing her in the car, it was actually Lori. We can discern this because the killer uses a birthday candle to ignite the gas and blow the car up. There was no way that Tombs would know it’s her birthday, so him being the real killer didn’t make sense.
Additionally, if Tombs was locked in the hospital there would be no way that he’d have time to attack Tree during the birthday party. The final clue is when Tree barricades herself in her room, only to be killed by the masked slasher. Only a student would have knowledge of the building and how to move through it undetected, so the killer had to be someone that Tree actually knew.
Happy Death Day also never fully explains how the reset cycle came to be, but one can view it as punishment for all of Tree’s actions. She was a terrible person to her friends and family up until the last few resets. We never learn if Tree just needed to survive the day and accept who she was to truly break the endless time loop. The fact that she was hunted down could be viewed as just bad luck or timing since it’s her death that causes the day to begin again. Sadly, we may never get a full answer as to why Tree was stuck in a never-ending loop, as it’s clearly up to the audience to determine what caused it.