Charlie Reade traces everything back to the Sycamore Street Bridge, where an icy skid killed his mother and sent his father, George Reade, into years of alcoholism. Charlie begged for a miracle and vowed to repay it; a Twelfth Step visit rescued George, who rebuilt his life. Years later, biking past a decaying Victorian, Charlie hears Radar, the feared German Shepherd of recluse Howard Bowditch, howling. He scales the fence, finds Bowditch with a shattered leg, calls 911, and promises to care for Radar. That promise binds them.

Charlie becomes Bowditch's right hand: feeding Radar, cleaning, installing safety bars, and learning pin care after a brutal external fixator goes on. Bowditch hires him from a flour canister stuffed with cash and odd reddish pellets. He sends Charlie to sell six pounds of pellets to jeweler Wilhelm Heinrich; the sale funds the hospital bill, but the gold, and Heinrich's subsequent murder, casts a shadow. Back home, Charlie secures Bowditch's Oxy, oversees physical therapy, and meets Melissa Wilcox, who hints at prostate cancer Bowditch refuses to treat beyond Lynparza. Radar falters; a house-call assistant provides harsh meds that trade time for comfort. Bowditch warns that gold inspires dangerous greed, then kills something in his locked shed after Radar raises an alarm.

Days later, Bowditch dies of a heart attack, having told Charlie to secure a wallet and key from under the bed and to call lawyer Leon Braddock. Charlie inherits the house, land, and Radar. After the funeral, he finds the house ransacked; a neighbor recalls a peculiar, sing-song magazine peddler. Police dismiss it as obituary thieves. A cassette in Bowditch's wallet changes everything: "Howard Bowditch" is Adrian Bowditch, born 1894, who found a "well of the worlds" beneath his shed leading to a cursed city, gold, and a turning sundial that grants youth. He marks a safe route and urges Charlie never to ride the sundial himself but suggests it could restore Radar.

Charlie verifies the shed's truth: a spiral of ancient stone steps and cat-sized roaches that crumble in Earth's air. He prepares the house while a sing-song intruder ambushes him: Christopher Polley. At gunpoint, Charlie opens the safe but spills the bucket of pellets, drops Polley, breaks his wrists, and spares his life. With a Chicago cover story planted for police and his father, Charlie packs supplies and descends the 185 steps with Radar into red poppy fields under a gray sky.

In Empis, Dora (Deerie), a kind, deformed shoemaker with Adrian's initials over her door, feeds them and sends Charlie to a "googir", the Goose Girl Leah, who has no mouth and speaks through her horse, Falada. Leah warns him: follow Adrian's AB marks, never speak certain names, and leave the city Lilimar before dark. She places the sundial behind the palace and directs him to her blind uncle, Stephen "Woody" Woodleigh, and deaf cousin, Claudia. Woody fills in Empis's fall: royals slaughtered, survivors cursed to lose senses, and a tyrant called the Flight Killer ruling with undead night soldiers and the giant Hana. Claudia tends Radar, gives precise infiltration instructions, and lends a quiet trike. Charlie rides into Lilimar at dawn, opens the colossal gate in Leah's name, and ghosts through a warping, haunted city by AB marks while rain lashes.

He slips past Hana's conjoined yellow houses into a palace plaza, finds an alcove where a mermaid, Elsa, is impaled, and reaches a vast sundial. He strains it counterclockwise until Radar leaps young and strong into his arms. On the way out, the marks vanish; Peterkin, a malicious dwarf, has erased them with lye. As night closes, Charlie navigates by a ruined monarch statue, flees rising dead in a cemetery, and opens the outer gate in Leah's name. He shoves Radar through to safety but is seized by night soldiers and dragged to Deep Maleen.

In the dungeon, frail cellmate Hamey explains the "Fair One," a lethal tournament requiring thirty-two "whole" prisoners. The Lord High, Kellin, interrogates Charlie with tea and threats, probing the sundial and gold and producing Polley's wallet. Charlie lies about his origin; Kellin sends him back and orders him shown the Belts, where enslaved grayfolk churn treadmills to power Lilimar. Practice reveals Elden Flight Killer, Leah's brother, as the monstrous ruler. In the gas-lit stadium, VIPs like Petra and looming Red Molly watch as Charlie defeats the favorite, Cla, by exploiting his side-blindness. Prisoners kneel to Charlie as "prince."

Covert ally Pursey, a gray trustee, slips notes revealing a hidden door from the Officials' Room. Claudia confirms Radar is safe via a red cricket (the Snab). A dream sparks Charlie's plan: water detonates the night soldiers' blue auras. At second-round muster, Jaya and Eris douse the guards; explosions shred the escort. The prisoners fight to the Officials' Room, topple a cabinet to expose a door, and dive into a tiled passage; Aaron dies when Charlie throws his last bucket. They surface at the Trolley House by the gate as Kellin advances with troops and Red Molly in a motor-wagon. Peterkin is swatted in half; Ammit dies attacking Molly; Charlie empties a .22 into Molly's mouth, and she chokes on her shattered teeth. A vast cloud of monarchs pours over the wall, short-circuiting the night soldiers. Kellin flees. At the gate, Radar careens into Charlie.

That night, allies gather. The moons are nearly kissing, a time when the Dark Well can open. Claudia says the wounded "snake" must be finished; Woody recalls Leah and Elden's past and Elsa's songs. Charlie follows Leah toward Lilimar. The Snab guides them to her, and Charlie swears Leah will judge Elden. At dawn they reenter via a hidden door. Charlie kills Hana; Leah beheads her. He shows Leah Elsa's corpse; Leah grieves and nods to kill the Flight Killer if Charlie falls. Inside, cooks report Pursey was taken. Past a desecrated reception hall and a damaged butterfly mosaic, they crank a lift skyward and enter a spiral stair.

The Snab perches on Radar. In Kellin's suite, Leah kills Jeff, then the Snab summons rats that overwhelm Kellin's aura and reduce him to bone. Jeff's poisoned blade kills Iota in Leah's arms; Leah vows, "The Queen of Empis will do her duty." Charlie detours to the torture chamber to free mutilated Pursey (Percival) and sends him out with Jaya. Leah leads Charlie, Eris, and Radar through wardrobe passages into ancient tunnels brightening with sickly green. Using Petra's silk, Radar tracks Elden to a colossal shaft under an alien sky, a derrick poised over the Dark Well as the moons meet.

Leah descends on Elden's palanquin. Bearers die or flee. Elden stands crowned and half-transformed, tentacles writhing. He opens the hatch; Gogmagog stirs. Tentacles seize Charlie and Leah. Leah slashes Elden's eye; a thorned wing hooks him into the well. The monster rises; Charlie forces it back by naming it, Gogmagog, again and again. Leah commands the hatch shut. Petra erupts from a palanquin and bites Charlie's forearm; Leah shoots her dead. The Snab brings fireflies to guide them up. In the plaza, sunlight breaks, and grayfolk kneel as Charlie proclaims Leah queen.

Charlie convalesces under Dora's care. Leah finally visits in white, admitting she long knew Elden's truth and that the sundial leaves riders barren. They acknowledge love but agree he must go home. After reconciling with Claudia and Woody, Charlie departs to cheers beneath monarchs and returns through the well to snowy Illinois four months later. He reunites with his father. Years on, he tells George the truth; together they visit Empis once and then seal the well with steel and concrete, setting Radar's pawprints in the slab. Charlie builds a quiet life, carries guilt over Polley's later murder, dreams of Red Hope, and keeps watch over a house that once held a door to another world.