Jayne Nighswander extorts Arthur, threatening his mother's life unless he steals rare books from Brooks Library.

Arthur steals the Enoch Crane journal, the library's most prized possession, and hands it over to Jayne.

Arthur and his friends perform the summoning ceremony and strike a deal with King Sorrow.

King Sorrow incinerates Jayne in California on Easter; Erin's parole is approved.

Gwen loses a riddling contest with King Sorrow and is forced to end her romance with Arthur.

Allie Shiner boards British Airways Flight 238 to try to prevent King Sorrow from destroying it.

Allie and Van kill Horation Matthews moments before King Sorrow reaches the plane; the flight lands safely.

Van and Donna McBride are abducted by the private security firm Thermopylae.

Van dies by suicide to guarantee Donna's survival from Thermopylae's threat.

Donna kills Valentine and summons King Sorrow to destroy the Thermopylae base.

Arthur draws the Sword of Strange Hangings from a crypt, but Colin fatally stabs him to preserve the King Sorrow arrangement.

Robin tells Gwen about Colin's betrayal; Colin preemptively names Gwen as the next sacrifice to King Sorrow.

Daphne Nighswander shoots Colin and Gwen; Tana kills Daphne to stop the attack.

The group performs a séance in the Brooks Library tower; Donna sacrifices herself to distract King Sorrow.

Gwen tricks King Sorrow into swallowing his own tail, destroying him, and is left critically injured.

Arthur Oakes is blackmailed into stealing rare books, which inadvertently leads his friend group to summon King Sorrow and enter a lifelong arrangement of annual sacrifices. As each member of the group grapples with the moral weight of the deal, King Sorrow's reach grows, touching the lives of strangers on a transatlantic flight and agents of a shadowy security firm. Van McBride's suicide and Arthur's murder at Colin's hands mark the arrangement's most devastating costs. The surviving friends rally around Gwen Underfoot, who discovers that Arthur left behind the knowledge she needs to finally slay the dragon. In a climactic confrontation in the college library tower, Gwen uses King Sorrow's self-indulgence against him and destroys him at great personal cost.

The headline events from summoning to slaying King Sorrow.

Arthur meets Gwen Underfoot at The Briars while she does a crossword, and the two share an instant connection.

Colin's grandfather Llewellyn screens a film documenting the military summoning of a murderous ghost named Elwood Hondo.

Jayne attacks Arthur and his friends on Halloween; Arthur confesses the extortion scheme to his group.

The group confronts Jayne and Ronnie and urges them to flee town before Easter to escape King Sorrow.

Arthur's friends stage a library break-in to create an alibi during his mother's parole hearing.

Gwen takes a job caring for Llewellyn Wren and gives up her enrollment at Rackham College.

After winning a second riddle against King Sorrow, Gwen names Llewellyn as the next sacrifice and serves him dragon tears.

Allie and Van reconcile and marry in the ruins of an old church in Greenland after surviving the Flight 238 ordeal.

The Black Cricket prison gas explosion kills Francine Trout, who is posthumously exonerated for Cady Lewis's murder.

Gwen and Erin fail to save a trapped woman named Wendy Arthur from the Black Cricket rubble as it collapses.

Arthur and Colin find the troll Svangur under Slaughterbridge and bargain with him to lead them to the crypt.

Gwen publicly confronts Colin about murdering Arthur and naming her as a sacrifice in front of their friends.

Allie infiltrates The Briars while Colin is away and steals the martyr's robe from the Cabinet of Curiosities.

Colin summons Elwood Hondo to kill Gwen's allies; Hondo turns on Colin and kills him instead.

Allie and Tana marry, and Gwen finishes editing the dragonslaying manuscript Arthur had written.

Behind the central conflict with King Sorrow lies a web of relationships, choices, and consequences that shape every character's arc. Arthur's accidental meeting with Gwen at The Briars and his confession of Jayne's extortion to his friends set the moral tone for everything that follows. Gwen's decision to forgo college and care for Llewellyn, and her hard-won victory in a second riddle against King Sorrow, establish her quiet centrality to the group long before she becomes its final champion. The destruction of the Black Cricket prison and the failure to save Wendy Arthur force Gwen to reckon with the true cost of the arrangement. In the final stretch, the theft of the martyr's robe, Colin's fatal miscalculation with Elwood Hondo, and the marriages of the survivors bring the long story to its bittersweet close.

The significant moments behind the main story's turns.

Arthur gives his hoodie to Tana Nighswander at Black Cricket prison, an act of kindness that sets the story in motion.

The friend group reads the Crane journal at The Briars and decides to perform the dragon summoning ritual themselves.

Serpent tattoos appear on Arthur, Gwen, and Van after the summoning, confirming King Sorrow's permanent mark on them.

The group shares a vision of King Sorrow stalking a terrified Jayne in her home before Easter.

King Sorrow reveals to Gwen that their deal requires a new sacrifice every Easter for the rest of their lives.

King Sorrow confronts Allie in the airplane lavatory and reveals she must personally kill Horation to save the flight.

The Oklahoma City bombing occurs, and Allie connects McVeigh's funding to Horation's extremist network.

King Sorrow possesses Donna during captivity and exposes Valentine's true identity as Norman Barclay.

Donna bites off Valentine's ear during interrogation, asserting her defiance against Thermopylae's captors.

Gwen rebukes Donna for the collateral deaths at Black Cricket; Donna remains unmoved even after Francine's exoneration.

Arthur and Colin debate the nature of God, suffering, and human goodness during their descent into the cave crypt.

A flashback reveals that during the summoning ceremony Colin secretly saw visions of his friends' deaths and his own rise to power.

Donna has a vision of Van's spirit, who rebukes her for the Black Cricket deaths and urges her to change.

Donna discovers Colin has secretly contracted Thermopylae for twenty years and defects to Gwen's side.

Robin assures Gwen that other good people will emerge to fight the new dragon causing global disasters.

Every major shift in King Sorrow begins with a revelation that reframes what came before and a decision that locks the characters into a new path. Arthur's casual act of generosity at the prison triggers a chain of coercion that ends with his friend group bound to a demon for decades. The discovery of King Sorrow's true terms, the exposure of Colin's long-running betrayal, and the supernatural visions experienced by Donna and Allie each represent moments where the characters must choose who they want to be. Colin's secret vision of his friends' deaths during the original summoning ceremony, only revealed much later, recontextualizes every manipulative choice he made in the intervening years. The pool closes with Robin's quiet, hopeful charge to Gwen to trust in the goodness of others — the moral cornerstone of the entire story.