The Frostbitten Earth is a story arc within a parallel universe, with the main plot being the attempt to reverse the event that created the parallel universe. This universe's existence was presumably ended when Haylee Warden destroyed the artifact responsible for the universe's creation. The primary POD (point of diversion) was Matt never existing, thus preventing The PAAB's discovery of the Glacier.
This universe is a parallel universe directly created by an individual. The world was mistakenly made when Austin jokingly wished that Matt had never existed. The wish was made in the vicinity of Loki's Loop, a CAMELOT artifact capable of granting such wishes.
This universe had one point of diversion, that PAAB-member Matt never existed, thus leaving the Glacier to approach Earth undiscovered and unstopped by anyone but The Order. This led to the consumption of Earth by the Glacier and the subsequent freezing of Earth.
The Earth becomes consumed by the Glacier.
The PAAB never existed, and all would-be members were presumably killed except for Mallory
Coach Hill's Black Sabbath never takes place, resulting in him becoming the leader of Ethel's survivors in a totalitarian camp ran by The Order.
AB is presumably killed before he becomes powered.
Ethel is buried under snow and ice, with survivors living inside the school.
At breakfast, Austin sarcastically wishes Matt had never existed after the latter bumped into him. Mrs. Hannah grants the wish, and Austin is transported to a parallel universe, with him passing out from the movement in subspace.
Once he wakes up, Austin finds the cafeteria empty and wrecked, with nobody around. He inspects the window and discovers it is frozen, making him realize the change in history. Austin rushes to the kitchen to try and find Mrs. Hannah, but instead finds Haylee Warden, who informs Austin that EHS is a survival base under the ice of the Glacier, and is led by the Order. Austin in turn tells Haylee about the wish and how things should be in his timeline.
A noise interrupts the conversation and the two hide behind a flipped table. When they think the thing that made the noise leaves, it dashes at them, revealing it is a preservoid. A brief fight ensues, and Haylee smashes the icicle of the preservoid, killing it. More come and the two run out of the cafeteria and into the ice-caverns that provide passage around EHS. Haylee escapes to safety, but Austin is killed by a group of preservoids.
Haylee holds a meeting with a group of people known as the Association (Haylee, Mallory, Ryan Molly, Scottie Corman, Adam Heron, Mrs. Burns, and Logan) and informs the group of what happened to her. The group decides to try and find the files on Mrs. Hannah, but they are located within the office, which is one of the most dangerous and preservoid-ridden areas in Ethel.
Haylee, Mallory, and Ryan set out into the ice-caverns, but are eventually attacked by preservoids and make a run for the office, barely managing to escape inside. Once inside, Haylee and Mallory find the files and discover that Mrs. Hannah' earring, Loki's Loop, can grant wishes, however Mallory is killed by Ryan, who reveals he works for the Order and is trying to prevent Haylee from ending the universe. A brutal fight erupts between the two, but it is unceremoniously ended by the now-preservoid Mallory shooting Ryan in the face. Mallory then aims for Haylee, who escapes the office and runs back to warn the others.
Along the way, Haylee finds a beaten Logan, who informs Haylee Adam was arrested and taken to the gym. Haylee rushes there to find Adam had been worshiping the Glacier and is to be publicly executed. Adam, in a fit of tears, reveals Haylee conspiring against the Order, hoping the information would spare his life. Scottie, however, commands the execution before Adam can reveal anything else.
Haylee attempts to escape, but is caught and dragged onto the makeshift stage to be executed. Here, Haylee notices Mr. Hill is wearing Loki's Loop, and Scottie slips her a knife to cut the ropes that bind her. Mrs. Bruns and Logan walk into the crowded gym, and Scottie whispers the last-resort plan to Haylee, who is also giving her final speech.
At the end of the speech, the four set the plan into motion, and Scottie kills Zack, Mr. Hill's right-hand guard, while Haylee cuts the ropes that hold her together. Mr. Hill, infuriated, hits Scottie off the stage with one of Adam's decapitated legs.
Meanwhile, Logan and Mrs. Burns break open the gym doors and Logan blows a whistle, attracting all nearby preservoids. Logan is killed by one of the first to rush in and the crowd begins panicking and running. Mr. Hill attempts to escape, but is caught off by Haylee. The Glacier catches onto Haylee's plan begins destroying Earth, causing the gym to collapse, which kills Scottie, many preservoids, and most of the panicking crowd still in the gym. Mrs. Burns rushes to protect Haylee, buying her time and killing as many preservoids and she can, but is eventually overcome and killed. As the gym collapses and ravaging preservoids rush to her, Haylee violently kills Mr. Hill and destroys Loki's Loop, sealing the universe and undoing the granted wish.
Austin is sent back to the point in time before the made the wish and almost repeats his lines, but is overcome by déjà vu. Matt puts Austin's attention back to Mrs. Hannah, to whom he asks for a biscuit. With his tray complete, Austin goes to sit with Matt, Jakob, and Jarod.