The season finale of It: Welcome to Derry starts with a deep fog descending upon the town. Pennywise is loose.
At Derry High School, the student body, excluding upperclassmen, is assembled in the gym. A spotlight hits the stage as Principal Dunleavy emerges, his movements stiff and unnatural.
The curtain opens to reveal Pennywise the Dancing Clown, using the principal as a puppet. He immediately discards Dunleavy, violently dismembering him in front of the students.
Pennywise sings and dances, ending his performance by showing the children the deadlights. The students fall into a suspended, catatonic state.
The milk truck
At the standpipe, Lilly, Ronnie, and Marge notice the fog rolling in. When they investigate, they find the structure plastered with missing posters of Derry’s children. It’s immediately clear Pennywise was never asleep.
They head to the school but find no students, only the principal’s body and a blood trail leading into town.
Among the posters, they find Will’s. With only one bike, they know they won’t catch up on foot. Nearby, the milkman lies dead. Every milkman has a truck.
Marge takes the wheel, and the three race after their friend.
Hanlon and Hallorann
Leroy rushes in the door ready to call and report General Shaw. However, the call is intercepted by a taunting Pennywise. Pennywise reveals he has Will.
Leroy heads to Dick’s quarters. He finds Dick with a gun in hand ready to end it all. He’s only stopped by Leroy pleading, saying that the creature has Will. The two men head to Rose’s house as General Shaw is informed of their departure.
At Rose’s, Dick can feel that the chill of the fog is unnatural. The group consisting of Leroy, Dick, Hank, Charlotte, Taniel, and Rose devise a plan. If Dick can use his ability to find the dagger, they would all have a fighting chance against Pennywise. They can rebury the dagger in an old tree just on the other side of the Penobscot River and reseal the cage.
Dick takes a herbal psychogenic tea and can see the girls riding in the milk truck with the dagger. He witnesses them crash the truck and continue on foot.
The dagger’s pull
The adults head out to find their kids and the dagger. Rose explains that the dagger alone can’t protect the children from Pennywise, and it will try to stop itself from going further from its home.
The effects of the dagger are seen as the girls walk along the blood trail. Lilly becomes convinced that the other two are just trying to use her, and she needs to run away. Ronnie and Marge manage to rip away the dagger, and Lilly’s senses return to her.
The dagger glows as Marge is holding it and the girls see the Penobscot River freezing over and the missing children suspended above the ice. Dick, still tracking them in his mind, tells the band of adults the new circumstances.
Rose fears they won’t make it to the tree before Pennywise crosses the river. So Leroy tells Dick to slow Pennywise down by creating a psychic link.
Marge Tozier
Will is found floating just behind the circus cart, leading the children. Pennywise opens the cart door to confront the heroes. Ronnie pulls the dagger out and Pennywise acts weakened by it momentarily. He then dashes around and disorients them. As they panic, Pennywise pulls Marge away from the group.
He taunts her, saying he can’t wait to taste Marge Tozier. When she hears this name, she’s confused. Pennywise states she’s not Marge Tozier yet. But soon she’ll be married and have a boy named Richie, who will kill him.
Pennywise explains he experiences time differently. He lunges to attack Marge but suddenly freezes.
Marge uses this to escape and reconnect with her friends. The children all suddenly fall from their suspended state and awaken. At the same time, the adults pull up in their car.
I’m not Bob Gray
Leroy and Taniel take the dagger from the kids and race toward the tree as the others try to rally the kids to safety. As they’re running, Taniel gets shot in the neck and Leroy is shot in the leg.
Will and the kids run to Leroy, who tells them to go to the old tree and bury the dagger. They set off using the fog as cover from the military. As the kids set off Shaw sees a frozen Pennywise.
Meanwhile, Pennywise wakes up around carnies, being told he’s Bob Gray. This is confusing for Pennywise as he also doesn’t seem to have his powers.
Shaw commands his men to apprehend Hanlon and Hallorann. When they get to the car and jostle Dick’s body it breaks the illusion created in Pennywise’s mind.
As Pennywise is awoken from his trance, he meets Shaw who tells Pennywise he is freed. Before Pennywise leaves, he sniffs the air. He recognizes Shaw as the boy from 1903 that escaped the forest. Pennywise takes the opportunity to devour Shaw.
Rich’s last stand
They run to the tree and are stopped by the dagger trying to force Will to turn around. Collectively, they use their force to push the dagger to the tree. Pennywise pursues the young heroes as they struggle to plant the dagger.
Leroy and Pennywise face off to give the kids more time. This results in Leroy being subjected to the deadlights.
As Pennywise gets closer, Dick looks across the mist and sees the ghost of the War Chief and behind her is Rich running to help his friends.
Against Pennywise’s best efforts, Rich reaches his friends in time and the dagger is put into the ground, reconnecting all the pillars. This sends Pennywise back to his long slumber, reawakens Leroy, and makes the fog begin to break.
The aftermath
Rich’s funeral is held giving everyone a sense of closure. Lilly sees her dad’s grave and Marge closes her chapter with Rich.
After, Marge and Lilly talk at the standpipe. Marge explains her conversation with Pennywise. She mentions how Pennywise experiences time differently. If Pennywise experiences time backwards, he may try to find one of their ancestors and try to stop his own death.
Meanwhile, the Hanlon family are packing up to leave Derry. Hank is taking Ronnie across the border with help from Rose’s friends. Will and Ronnie seal their goodbye with a kiss.
Rose makes an offer. It’s too difficult to run her sheep farm without Taniel so she’s selling it along with the house. Charlotte and Leroy would be good gatekeepers for Pennywise. After some thought, the family agrees to stay
Ingrid Kirsch is now a resident in Juniper Hill. 26 years pass when she hears a commotion in the hall. She finds a distraught Beverly Marsh with her father weeping at the sight of Mrs. Marsh’s lifeless body. Ingrid reminds everyone, no one who dies in Derry ever really dies.