Nico identifies the voice in his recurring dreams as Bob the Titan, calling for help from Tartarus.

Rachel Dare delivers a prophecy telling Nico he must find who calls to him and leave something of equal value behind.

Chiron officially assigns Nico and Will a quest to rescue Bob from Tartarus.

Nico and Will visit Percy and Annabeth at Sally Jackson's apartment to gather advice about surviving Tartarus.

Nico and Will arrive at the Door of Orpheus in Central Park and Will sings to open it.

Epiales, the demon of nightmares, traps Nico and Will in a repeating nightmare cycle at the entrance to the Underworld.

Will discovers a new power and shoots a beam of pure light to destroy Epiales.

Screech-Bling welcomes Nico and Will to the troglodytes' underground cave city beneath the River Styx.

Nico and Will sneak into Persephone's garden to steal pomegranate fruit as payment for Menoetes.

Nico and Will descend into Tartarus over the Acheron falls in Gorgyra's boat.

Nico summons the skeletons of Tartarus to form a bone ramp, slowing their deadly fall to the ground.

Small Bob finds Nico and Will in Tartarus and begins leading them toward Bob's location.

Will and Nico combine their powers to shatter Bob's regeneration blister and free him from Nyx's trap.

Nyx's own children revolt against her and restrain her so Bob and the demigods can escape.

Bob pilots Gorgyra's boat out of the Underworld and arrives at Camp Half-Blood.

Nico di Angelo identifies the mysterious voice in his dreams as Bob the Titan, triggering a desperate quest to rescue him from Tartarus. Armed with a prophecy from the Oracle and an official quest from Chiron, Nico and Will Solace seek counsel from Percy and Annabeth before descending through the Door of Orpheus. After breaking free from the nightmare demon Epiales, they find allies in the troglodytes and fight their way toward the Acheron falls. Descending into Tartarus itself, they track Bob with Small Bob's help and combine their powers to shatter the regeneration blister imprisoning him. Nyx's own children turn against her, allowing the group to escape up the river and return to Camp Half-Blood.

The headline quest: from prophecy to Tartarus and back.

Will names Nico's condition as PTSD and suggests he consult Mr. D, and Nico begins daily morning sessions.

Nico and Will bid farewell to Will's siblings Austin and Kayla as they leave Camp Half-Blood for the year.

On the train to Manhattan, Will shares cheerful travel stories while Nico reflects on the painful side of being a demigod.

Nico and Will are expelled back to Central Park every time they attempt to pass through the entrance to the Underworld.

Nico recounts his previous solo descent into Tartarus in full to Will and the assembled trog council.

Nyx appears in Nico's dream disguised as Bianca and shoots him with an arrow that wounds him in real life.

Will gives his sunlamp to the timid trog Hiss-Majesty, who gains confidence wielding the light of a child of Apollo.

Nico and Will reveal they are gay and bisexual to Menoetes, winning his trust and securing safe passage.

Nico and Will fight two fire-breathing drakons alongside the troglodytes Hiss-Majesty and Screech-Bling.

Will accidentally punctures a regeneration blister in Tartarus, releasing Stymphalian birds that carry him into the air.

Will misdirects the compulsive spirit Amphithemis by falsely claiming the cynocephali have taken Dionysus.

Nico and Will argue over Will's deceptive treatment of Amphithemis, then reconcile by acknowledging their individual mistakes.

Will and Nico reach Gorgyra and learn she collects souls whose greatest crimes were against themselves.

Nyx introduces the cacodemons she crafted from personifications of Nico's darkest emotions and most painful memories.

Nico sends an Iris-message to Piper McLean to apologize for withdrawing from her after Jason's death.

Before the quest begins, Will helps Nico name his PTSD and encourages him to seek daily support from Mr. D, laying a foundation of care between the two. The journey is full of setbacks — getting expelled from the Underworld entrance repeatedly, fighting drakons, and becoming separated by monstrous birds — but each obstacle deepens their bond. Crucial allies like the troglodytes, Menoetes, and Gorgyra offer help in exchange for honesty and storytelling, rewarding Nico and Will's openness about who they are. In Tartarus, Will's deceptive handling of the spirit Amphithemis becomes their sharpest conflict yet, but they repair it with genuine accountability. After defeating Nyx and returning to camp, Nico reaches out to Piper McLean to begin healing a friendship neglected by grief.

The journey's key moments: allies, obstacles, and hard-won trust.

Nico is forced to relive the moment Cupid outed him in front of Jason in a vivid PTSD nightmare.

Nico confesses to Will and the trogs that he personally encountered Nyx during a previous solo descent into Tartarus.

Nico recounts how the goddess Nemesis gave him pomegranate seeds and warned him to avoid 'Mother' during that earlier Tartarus visit.

Nico recounts how giants Otis and Ephialtes captured him and imprisoned him inside a large jar during his solo descent.

Persephone freezes Nico outside her garden and confronts Will alone about why he is stealing her fruit.

Persephone shows Will a flower that only blooms in darkness, and it opens in his hand revealing his inner darkness.

Persephone tells Will to stop trying to fill Nico with light and instead offer Nico his own darkness.

Menoetes reveals he wants the pomegranates for his boyfriend Geryon, who has reformed since his battle with Percy.

Nico tells Gorgyra the story of how he publicly asked Will on a date in front of the entire camp.

Will tells Nico that his public coming out gave other LGBTQ+ demigods at both camps the courage to live openly.

Nico guides Will through the primordial darkness of Chaos by having Will hold onto him and trust him completely.

Nico orders the cacodemons to stop attacking Will and discovers he has authority over his own demons.

Will channels his inner darkness and uses Apollo's power to bring illness, afflicting Nyx with debilitating hay fever.

Nyx tries to reach the escaping boat but withers into a husk when her body touches the Acheron.

Will apologizes to Nico for trying to heal his darkness rather than accept it, and the two fully reconcile.

The deepest emotional shifts in the novel flow from a series of revelations that force Nico and Will to confront who they truly are. Nico relives the trauma of being outed by Cupid, then chooses to share his terrifying previous Tartarus descent in full — including his encounters with Nemesis and the giants who imprisoned him in a jar. Persephone's garden becomes a site of transformation when she shows Will a darkness-blooming flower opening in his own hand, shattering his belief that he holds no darkness within himself. The stories shared with Gorgyra carry their own revelations, as Nico's public coming out is shown to have inspired a wave of LGBTQ+ demigods at both camps. In the final confrontation, Nico discovers he controls his own demons, Will weaponizes his darkness for the first time, and Nyx is destroyed by her own refusal to change.