What actually happens
Ryan's reactor has a few side effects
On September 19, Ryan Phan wakes up in his car and goes back to his dorm, where he finds his roommate Carter with Carter's girlfriend, Tree. Ryan is building an experimental quantum reactor with Samar and Dre, meant to slow down time. Dean Bronson shuts the project down after it causes power outages and has produced nothing practical, and then someone in a Babyface mask murders Ryan, who wakes up on the 19th again. Tree tells Carter and Ryan about reliving September 18th, and they agree to help Ryan. They work out that the reactor started the loop. The killer finds Ryan, but when Tree pulls off the mask there is a second Ryan underneath, who says the first one has to die to end the loop. Frightened, Ryan switches on the reactor, and an energy pulse knocks everyone out.
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Tree wakes up in a different September 18th
Tree comes to in Carter's room on September 18th and replays her original loop, but this time Carter is dating Danielle. Ryan thinks the reactor pushed Tree into another dimension. Her mother is alive in this one, and Tree would like to stay. That night she goes to the hospital to catch the serial killer John Tombs before he gets loose, but a police officer stops her first. The killer kills the officer, and Tree meets Lori at the elevator and sees that in this reality Lori is not the killer. Lori says it cannot be Tombs, because she has only just brought him in for an operation. The killer stabs Lori and chases Tree up to the roof, where she falls to her death by accident. That is the scene people dread most, and it comes in the middle of the movie. Tree wakes at the start of the loop again and demands that Ryan's team help her get out of it, which means testing dozens of algorithms.
Homework, but Tree has to die to hand it in
Carter suggests that Tree be the group's recorder, so she ends every day by killing herself, which resets the loop for the next test. After enough days the damage adds up and she collapses. She wakes in the hospital, steals a gun to go after Tombs, and finds Lori already dead. Tombs attacks her in a Babyface costume, and Tree shoots him. A second Babyface killer shows up, so Tree kills herself and the killer together. The group eventually finds the right algorithm, but a technical problem delays it. Tree decides to stay in this dimension, and Carter tells her to consider the cost of living a life that is not hers. Then the news reports that Carter was lost at the hospital while trying to rescue Lori, and Tree blows up a power station to shut the reactor off and save them both. The loop restarts, and she chooses to return to her own reality. Before leaving she advises Lori to break off the affair she is having with Gregory Butler, her professor, finds out Danielle is seeing someone behind Carter's back, and says goodbye to her mother.
The ending, explained
Before the group can use the reactor, Bronson takes it away, and Tree, who thinks she is too weak for another loop, insists they get it back. Danielle distracts Bronson while the others take it. Tree goes to the hospital to save Lori from Tombs and is cornered by the second Babyface killer, who is Gregory, trying to bury evidence of his affair with Lori. His wife Stephanie appears and shoots Lori, which shows she is in on it, but Gregory turns on her and kills her too. Tree outwits Gregory and kills him. Lori survives. Tree and Carter kiss as the reactor starts up, and Tree is sent home to her own dimension, arriving on September 19. Later, agents take Tree, Carter, Ryan, Samar and Dre to a DARPA laboratory, which now holds the reactor for further tests. They need a test subject, and Tree offers up Danielle, who comes to in her room, screaming.
The post-credits ruling
Nobody has confirmed either way whether there is a scene after the credits.
✓ Spoiled safelyDog status: fine, no dog dies.
Questions people ask at 1am
Is Happy Death Day 2U scary?
Barely. Happy Death Day 2U is a 3 out of 10 with low dread, mild jump scares and not much gore, and it plays mostly as a sci-fi comedy.
How does Happy Death Day 2U end?
Tree kills Gregory, the second Babyface killer, and Lori survives. The reactor sends Tree back to her original dimension, and agents later take the group to a lab and a test subject screams.
Does the dog die in Happy Death Day 2U?
No. No dog dies in Happy Death Day 2U.
Is there a post-credits scene in Happy Death Day 2U?
Nobody has confirmed whether Happy Death Day 2U has a scene after the credits, so there is no reliable answer.
Who is the killer in Happy Death Day 2U?
Happy Death Day 2U has more than one Babyface. Early on it is another version of Ryan, later John Tombs wears the costume and Tree shoots him, and the second Babyface killer is Gregory Butler, a professor hiding his affair with Lori.
