Landon says there was actually a point in pre-production when Universal was asking for an exact reason for the time loop; however, he fought back. He liked the lingering mystery, which, along with Tree's roster of haters, keeps viewers guessing till the end. If she stops her murder, does she stop the loop? "For me, it was about making sure there were enough credible red herrings and suspects," Landon says.
Unmasking the killer becomes a seemingly impossible task, as everyone around Tree looks like they could be out for some sort of revenge. It's fair to think Tree's love interest, Carter, could be guilty, for example. He's introduced as a spurned one-night stand with unclear intentions, and we don't immediately get his full back story. Same with Tree's professor fling, Gregory. And her other ex-fling. And her scores of sorority sisters. And, perhaps, the biggest red herring of them all: the murderous inmate being treated in the on-campus hospital. But after preemptively killing the inmate, Tree still wakes up on her birthday. It's a tragically comic gut punch, one that might make you ask, "Wait, why?" as it sends Tree back into her nightmare.
Tree's roommate, Lori -- initially the most innocuous of those in her inner circle -- is to blame. She's jealous of Tree's romance with Gregory. So she funnels her hatred into the poisonous cupcake Tree's gifted time and time again. Why did she die after killing the inmate? Tree finally pieces the puzzle together after the fake-out happy ending: The last thing she did before falling asleep was share the cupcake with Carter.
Solving the mystery and thwarting Lori stops the time loop, but it still doesn't fully explain why it happened. For that burning question, you'll have to hang your hopes on the future, like Lobdell and Landon.
"If I'm so lucky to get to make a sequel, and we would never count our chickens and I have no idea what's going to happen with this movie, I have the sequel ready," Landon says with a laugh. "It gets into the [time loop's] why, in a very, very, very, very specific way."