The fourth installment of HBO Max’s horror prequel It: Welcome to Derry (streaming now) has finally answered the question every Stephen King fan has asked since 1986: why does Pennywise the Dancing Clown never stray beyond the Derry town limits?Turns out the shape-shifting entity isn’t just evil—he’s grounded. Literally.A Falling Star, A Living NightmareSunday’s episode opens with a celestial impact in the year 978 A.D. A meteor-like object screams across the sky and burrows into the land that will one day become Derry. The indigenous Shokopiwah tribe rushes to the crash site and finds a writhing, light-sensitive horror trapped inside the molten hull.Tribal elders quickly realize the creature—later dubbed “IT”—feeds on fear and can morph into any nightmare it reads from human minds. Their solution: build an unbreakable cage using shards of the same black star-metal that brought IT to Earth. The fragments act as a mystical force-field, locking the entity inside a invisible perimeter that future settlers will unknowingly call “Derry.”The Barrier That Built a TownColonial-era flashbacks reveal English settlers ignoring Shokopiwah warnings and founding a village directly atop the containment zone. Each generation suffers IT’s 27-year feeding cycle, but no one understands why the monster never follows fleeing victims past the city-limit sign—until now.“Every missing poster, every blood-filled sewer grate, it’s all because a long-dead tribe did too good of a job,” showrunner Jason Fuchs says in HBO’s behind-the-scenes featurette. “Derry exists because the prison exists.”Modern Heroes, Ancient StakesIn present-day 2025 timeline, psychic chef Dick Hallorann (returning from King’s The Shining universe) races to recover the scattered black fragments before a real-estate developer’s excavation project accidentally cracks the barrier. If even one shard is removed, Pennywise could go global.Episode 4 ends on a chilling reveal: the House on Neibolt Street—future lair of the Losers Club—sits directly above the original impact crater, meaning every nail, every floorboard, every clown-shaped shadow is soaked in cosmic-grade evil.Critical and Fan ReactionEarly metrics show It: Welcome to Derry Episode 4 spiked HBO Max streaming numbers by 38% overnight. Rotten Tomatoes audience score sits at 91%, with critics praising the blend of indigenous folklore and sci-fi horror.“Finally, a prequel that adds to the mythos without breaking it,” writes Bloody Disgusting. “Pennywise isn’t just a clown; he’s a cosmic refugee, and Derry is his Guantánamo Bay.”What’s Next?Four episodes remain in the eight-episode first season. Teasers hint that Hallorann’s quest will collide with young Mike Hanlon’s ancestors, setting up the oral-history tradition that eventually guides the Losers Club in the 2017–2019 films.New episodes of It: Welcome to Derry drop every Sunday at 9 p.m. ET exclusively on HBO Max.Key Questions AnsweredCan Pennywise leave Derry? Not without destroying the black-star fragment grid—something Episode 4 proves is easier said than done.Are the fragments sentient? They glow when IT is near, suggesting a residual link to the creature’s home dimension.Will Bill Skarsgård appear again? Producers confirm the actor will reprise his role in the season finale, promising “the most accurate book-to-screen transformation yet.”Stay tuned to our It: Welcome to Derry episode guides.