Will is urgently whisked to the lab, his mind reeling as he fails to recognize the familiar faces of Bob, Hopper, or Owens. Owens voices his concerns, theorizing that tampering with the tunnels might pose a mortal danger to Will. He guides Hopper down to the basement of the lab, where they uncover an astonishing revelation: an immense gateway to the Upside Down, lurking beneath the floorboards, waiting to be unleashed.
Dart undergoes another transformation, shedding its skin and escaping the confines of the root cellar. Nancy and Jonathan spend a tender night at Bauman's, confessing their mutual feelings for each other in the warmth of the moment.
Lucas is determined to vindicate his tale to Max, sneaking her out of her house in a daring escape. Steve, Dustin, Lucas, and Max set up a trap for Dart at the junkyard, but their plan backfires when Dart, now swollen to the size of a hulking dog, arrives with a menagerie of teenage Demogorgons. They corner the quartet inside a bus, trapping them in a perilous situation.
In a moment of clarity, Will announces that he knows the key to vanquishing the Shadow Monster. Owens dispatches a team of soldiers into the treacherous tunnels, but the Demodogs abandon the junkyard, their noses twitching in the direction of fresh prey. Will offers a begrudging apology, revealing that the Shadow Monster had coerced him into betraying them. The Demodogs launch a surprise attack on the unsuspecting soldiers, slaughtering them mercilessly before scaling their way into the lab.
