WARNING: Spoilers ahead for Happy Death Day 2U.

Happy Death Day 2U’s ending not only revealed the reason for the time loops that force Tree Gelbman (Jessica Rothe) to repeat the same day multiple times but it also set up a multiverse and a third film. Written and directed by Christopher Landon, the sequel immediately picks up after the events of the first Happy Death Day where Tree solved her own murder and freed herself from being trapped in a time loop.

While the first Happy Death Day was a straight-up horror-slasher film mixed with Groundhog Day’s gimmick of the main character repeating the same day over and over, Happy Death Day 2U is even more genre-bending. The sequel retains its serial killer, the masked Babyface Killer, but backburners its horror elements. Instead, Happy Death Day 2U is more of a Back to the Future Part II-inspired sci-fi comedy involving parallel universes. The switch in genres is by design since producer Jason Blum wants each Happy Death Day movie to be different.

However, Happy Death Day 2U is incredibly ambitious with its complex story. As the trailer indicated, Tree is once again forced into a time loop, but it also deceptively claims the Babyface Killer is now after “all of us” and that isn’t the case; the advertising hides the film’s real story that Tree is also trapped in a parallel universe. If Happy Death Day 2U left you scratching your head, here’s our explanation of the time loops, the multiverse, and everything else in this crazy sequel:

  • This Page: Happy Death Day 2U’s Time Loops & Parallel Universes Explained Page 2: Happy Death Day 2U’s Killer & Ending Explained Page 3: How Happy Death Day 2U Sets Up Part 3

Happy Death Day 2U’s Time Loop Explained: Origin And How They Really Work

Happy Death Day 2U reveals the cause of Tree’s time loop right away: it was all because of a device called the Sisyphus Quantum Cooling Reactor. While the events of the original movie were occurring, Carter’s (Israel Broussard) roommate Ryan (Phi Vu) and his lab partners Samar (Suraj Sharma) and Dre (Sarah Yarkin) were working on their science project at Bayfield University’s Science and Engineering building. Their device, which they named “SISSY” for short, was designed to slow down time. But they couldn’t get the algorithms right and instead, SISSY created a time loop that somehow trapped Tree (SISSY’s malfunctions are also responsible for the rolling blackouts that plagued the campus in the first film).

In Happy Death Day, Tree’s time loop forced her to relive her birthday, Monday, September 18th, which always ended with her being murdered. After dying eleven times by her count, Tree saved and freed herself when she figured out that it was her roommate Lori (Ruby Modine) who was behind the plot to kill her; when Tree killed Lori, she closed that time loop and Tree was able to move onto the next day. It looked like Tree killing her own killer broke the time loop, but that’s not quite accurate.

Tree surviving the day instead passed the time loop onto Ryan, who began repeating Tuesday the 19th at the start Happy Death Day 2U. Ryan had his own Babyface Killer who murdered him, which reset the day when Ryan died. Luckily, Tree knew exactly what was going on (to her chagrin) so she, Carter, and Ryan set out to find the new Babyface. When Tree saved Ryan, they unmasked Babyface and were shocked to find he was a doppelganger of Ryan. Ryan II thought killing the other Ryan was the only way to stop the time loop, so that’s why he was killing “himself”. Why Ryan II choose to wear the Babyface Killer mask and behave like a serial killer, who knows?

Ryan II also knew SISSY was unstable but Ryan activated it anyway; the device’s faulty algorithm caused an overload that hit everyone in the lab - but it was Tree that was most affected. She was sent back to September 18th and into a new time loop - only this time, Tree also ended up in a parallel dimension. There, the rules for the time loop are the same: Tree has to die to reset the day, but this time, she’s not the target of the Babyface Killer so she has to commit suicide to force a reset.

Happy Death Day 2U’s Multiverse Explained

It turns out, Happy Death Day exists in a multiverse! Most of Happy Death Day 2U occurs in an alternate dimension where Tree has been sent by SISSY’s malfunction, which has a variety of big differences to the world she knows. The biggest is her roommate Lori (who is now dead in the original film’s universe) is the victim who gets murdered by the Babyface Killer; part of Tree’s ordeal is trying to save Lori and each time she fails, she has to die to reset the day and try again, either by making herself the new Babyface’s target or by finding creative means to commit suicide.

The full ramifications of the multiverse and Tree’s traveling to a parallel dimension are unclear. Tree replaced the alternate version of herself, telling Carter, Ryan, Samar, and Dre that she was both in a time loop and from a different reality. Otherwise, no one noticed Tree was from another universe, not even her parents.

The biggest unanswered question here is what happened to the “other” Tree. Did that Tree take “prime” Tree’s place in the first movie’s universe, with both trapped in a simultaneous time loop in two concurrent universes (one that only Tree Prime can break them out of)? Or did Tree II get pushed into a third universe, which created a domino effect across the universe? Given Happy Death Day 2U’s ending, this doesn’t seem to be something the movie is too concerned with.

How Happy Death Day 2U’s Parallel Universe Was Different

Happy Death Day 2U’s mirror universe is almost completely identical to Tree’s “prime” universe except for three key differences: First, Lori is still alive and she is the Babyface Killer’s target rather than the person behind the mask. This is because in this universe, Tree never had an affair with her professor Dr. Gregory Butler (Charles Aitken) at the same time Lori was sleeping with him. Therefore, Tree and Lori are actually close friends. Second, Tree’s sorority sister and frenemy Danielle (Rachel Matthews) is Carter’s girlfriend. Finally, in the parallel universe, Tree’s mother (Missy Yager) is also still alive.

Tree actually prefers living in the parallel universe; even though Carter is dating Danielle, Tree is overjoyed to have her mom back. In Happy Death Day, being forced to relive the same day repeatedly forced Tree to realize that she had grown into a terrible person after her mom died three years prior. However, Tree also gradually came to understand that she doesn’t belong in the parallel universe; her mother had three years of memories with the “other” Tree that “prime” Tree doesn’t have - and she’s living someone else’s life. Ultimately, Tree had to let go of her mother all over again and she chose to return to her universe to be with Carter.

Page 2: Who Were The Babyface Killers And How Did Tree Break The Time Loop?

All The Babyface Killers In Happy Death Day 1 & 2U

In both Happy Death Day films, there are actually multiple Babyface Killers. In Happy Death Day, the Babyface Killers were Lori and John Tombs, the serial killer who was admitted to Lori’s care at Bayfield Hospital, and each of them killed Tree multiple times. Lori hated Tree because Tree was a bad roommate and they were both having an affair with Gregory; she wanted Tree dead to have Gregory all to herself. John Tombs was both Lori’s backup to kill Tree if Lori couldn’t and Lori’s scapegoat.

In Happy Death Day 2U, the Babyface Killers were Gregory and accomplices: John Tombs and his wife Stephanie (Laura Clifton), along with the earlier Ryan II. Gregory took a page from Lori’s playbook in the first Happy Death Day and set Tombs free to be the scapegoat as Lori’s murderer. Gregory and Stephanie were both working to murder Lori because she was having an affair with Gregory (although Gregory also wanted Stephanie dead so he could be single and his ultimate plan was to off both his mistress and his wife). So, in both universes, Lori has an affair with Gregory but in Happy Death Day 2U’s alternate universe, Tree isn’t in the tryst and Gregory doesn’t even know who Tree is.

How Happy Death Day 2U’s Ending Closed The Loop

As September 18th kept repeating in Happy Death Day 2U, Tree split her time in the alternate universe to accomplish several goals: she wanted to spend time with her mom; she wanted to save Lori, and she had to learn Quantum Mechanics. Because Tree is the only one who retains her memory after the day resets, it was up to her to learn all and fix all of the complex mathematical equations and then teach it back to Ryan, Samar, and Dre so they could fix SISSY. Eventually, thanks to her “crazy memory”, Tree did learn all of the math required and they were able to perfect the algorithm and get SISSY to work properly.

Originally, Tree wanted SISSY repaired so they could use it to close the time loop but keep Tree in the parallel universe so she could stay in the world where her mom was still alive. However, Tree eventually realized she doesn’t belong in that universe and she chose to return to her own where Carter was her boyfriend. Tree also had to face the fact that if she stayed in the parallel dimension, everyone the Babyface Killer kills - Lori, the security guard, and Carter - stays dead. With Carter’s help, Tree manages to save Lori and expose Gregory and Stephanie as the Babyface Killers, setting everything right in the “other” universe just as Ryan and co. activate SISSY, releasing a quantum bubble that blew Tree back to her proper universe.

She woke up right back at the moment when SISSY malfunctioned in her original universe, meaning everything that happened to Tree in the parallel world took place in a split second to everybody else. It was (once more) Tuesday, September 19th so she was, again, free of the time loop and back in her own universe where she belonged. The loop is closed, seemingly for good.

Page 3: How Happy Death Day 2U Sets Up Part 3

What About Happy Death Day 2U’s Second Ryan?

While Happy Death Day 2U’s ending resolves most of its big questions, there’s still the question of Ryan’s doppelganger: where did he come from and what happened to him after? He said he was trapped in a parallel time loop but was he from the parallel universe that Tree spent most of Happy Death Day 2U in or the future of the original universe? It would make sense that he was from the future since he was dressed up as the Babyface Killer, so he knew about Lori and John Tomb’s attempts to kill Tree and used the same costume and methods to kill the other Ryan. He would also know SISSY would malfunction and he thought killing the other Ryan would close the loop. If he was from the parallel universe, he somehow retained no memory of his time in the loop when Tree crossed over.

Either way, Ryan II disappears entirely at the end of Happy Death Day 2U, likely a result of SISSY’s malfunction or successful firing. Still, where he came from and how his story resolved remains a big question going forward.

Happy Death Day 2U’s Mid-Credits Scene Sets Up Part 3

Happy Death Day 2U has a mid-credits scene that sets up a third movie. It’s still Tuesday, September 18th and Tree, Carter, Samar, and Dre are being forced to clean up trash around the Bayfield campus as community service - this is their punishment for defying Dean Bronson’s (Steve Zissis) orders not to turn on Sisy, which he wanted to be confiscated. Suddenly, Black SUVs belonging to DARPA (Defense Advanced Research Projects Agency) arrive and Dr. Parker (Kenneth Israel) orders the four college students to come with him. Upon arriving at DARPA headquarters, Dr. Parker reveals that he has brought the SISSY machine to his lab and they want to use it to test the time loops. Tree volunteers a new guinea pig for the experiment: Danielle, who wakes up in her bed screaming, presumably because she is now trapped in her own time loop.

This is a big clue to the plot of Happy Death Day 3, which director Christopher Landon says he has a “really bonkers and fun” idea for since he “always imagined Happy Death Day as a trilogy”. Despite Danielle being set up as the time loop’s new victim, somehow it will surely all come back to Tree literally having to save the day. It remains to be seen if the final film can top the sheer zaniness of Happy Death Day 2U - or if the world is ready for what’s to come in Happy Death Day 3 (which could even part of a Blumhouse shared universe).

Next: Why Blumhouse’s Dark Universe Reboot Will Be A Success

  • Happy Death Day 2U Release Date: 2019-02-14