Rexall Bridger sits in his living room watching two stacked television screens connected to his secret surveillance system at Henderson High and a camera at the pier. He drinks beer and listens to Tupac Shakur, mourning his dead friends, Clate Rodgers and Tab Daniels. Tab’s body never surfaced from the lake, and Rexall believes he will return. On the pier camera, Rexall sees a large dark figure he mistakes for the resurrected Tab. When he touches the screen, a blue spark arcs to his finger.

At the pier, Hardy cleans snow from his daughter Melanie’s memorial bench. He reflects on his wife Trudy’s death, Jennifer saving Proofrock, and a secret deal he made with the lake to spare Jennifer’s life after her suicide attempt. Mr. Armitage arrives on cross-country skis and sits with Hardy, asking about the 2015 massacre. Hardy notices blood on Armitage’s glove; Armitage claims he was painting a fire hydrant at Terra Nova.

At Pleasant Valley, Jennifer steals a key to visit Ginger Baker, who is bald after pulling out her hair. Ginger dons a handmade Hannibal Lecter mask and offers to be Jennifer’s informant in exchange for revenge against her sister Cinn for leaving her in the yacht. She reveals that before the massacre, she and Cinn believed they had captured Stacey Graves on a trail camera, though the footage was lost. After the massacre, they revisited the lake and found a fleshy mass under the pier, which Cinn fed until it grew into a new Lake Witch, now hidden at Terra Nova. Jennifer dismisses this as a lie inspired by the movie Hellraiser. Ginger taunts Jennifer, saying she has become the disbelieving adult who always dies in slasher films.

At the Henderson High gym, Jensen, Wynona Fleming, and Abby Grandlin play strip-HORSE by candlelight. Jensen falls and bleeds from behind his ear. Abby leaves to get supplies but returns with severe injuries to her face. An unseen attacker kills Wynona. Jensen flees through the halls toward the metal shop but is struck from behind with a toilet tank lid. The blow sends him forward, impaling him through the back on the antlers of a mounted bull elk. Dying, he sees his attacker and recognizes them with surprise.

Galatea presents a chronological history of violence in Proofrock: Glen Henderson’s 1878 murder of Tobias Golding and the legend of the Golden Pickaxe; Preacher Ezekiel’s 1915 drowning of his congregation and his sanctioning of the murder of Stacey Graves’s mother by her husband, Letch Graves; the 1920 creation of the Lake Witch legend after boys threw eight-year-old Stacey Graves into the lake, claiming she ran across its surface; the mysterious 1934 deaths of elk hunters during the Great Depression; the 1964 Great Idaho Fire that killed wildlife attempting to cross the dam; the 1965 Camp Blood murders by Amy Brockmeir; Melanie Hardy’s 1993 drowning; and the 2015 “Lake Witch Slayings,” Jennifer’s preferred term for the events, which includes victims not officially counted in the more narrowly defined “Independence Day Massacre.”

Galatea notes that masks of Dark Mill South are already being sold and speculates on who will become Proofrock’s next boogeyman. The report concludes by invoking Karl Marx’s idea that history repeats first as tragedy, then as farce, suggesting Proofrock needs time to grieve rather than create new monster myths.

A severely injured Abby Grandlin awakens in the gym and crawls toward her phone.

At the sheriff’s office, Letha watches a figure in a blue parka through the window. Mistaking him for Dark Mill South, she takes Sheriff Allen’s shotgun and fires. The recoil triggers two accidental discharges, destroying the door and overhead awning. When the figure sheds his parka, he is revealed to be Rexall. Letha goes inside as the phone rings; Abby is calling to report that everyone at the gym is dead, adding that she believes she is dying too.

Banner and his friend, Lonnie Chambers, struggle to subdue the agitated Rexall. Lonnie approaches with a squeegee frozen in a block of ice, intending to smash Rexall’s head, but Banner shoots the ice, shattering it. Jennifer arrives on a snowmobile, reporting three deaths at Pleasant Valley. The corpse of the third victim, Philip Cates, was staged to resemble a death from Black Christmas. Rexall taunts Jennifer, claiming her father Tab has returned. After Letha fires a warning shot, they decide to lock up Rexall and help Abby.

When Banner, Jennifer, and a physician named Doc Wilson reach Henderson High, they find the doors are locked. Banner’s pistol is also missing from his holster. Jennifer drives the snowmobile through the glass entrance, secretly pocketing the kill switch after Banner removes it. She enters the classroom of her former history teacher, Mr. Holmes, and mourns his death, writing his name in Sharpie in the corner of the chalkboard as a small memorial. She discovers Jensen’s body, recognizing the manner of his death from Silent Night, Deadly Night. Banner and Doc Wilson find Wynona’s body in the gym and tend to the barely alive Abby.

Jennifer and Banner unlock Abby’s phone with her thumb. Jennifer calls Cinn, who confirms she is at the nursing home and dismisses Ginger’s story about the creature under the pier. Jennifer informs Cinn about the deaths, indicating that South may be targeting her and her friends for an unknown reason. She gives Cinn survival advice before the call drops. Jennifer wonders if Ginger’s story might be true: Stacey Graves may have regenerated from the fleshy mass. She decides she must investigate Terra Nova to rule it out. She sends Banner on a futile search for the kill switch, then sprints toward the front of the school to take the snowmobile across the frozen lake.