The narrative jumps back four months to Hallowmas of the Autumn of Three. The Wundrous Society is hosting the Black Parade, a celebration of Hallowmas. Nightbeacons (candles that attract the restless dead) are lit from the fireblossom trees that Morrigan Crow previously brought back to life using the Wondrous Art of Inferno. Morrigan discusses what the Black Parade entails with friends in her class, Unit 919, which includes Cadence Blackburn, Hawthorne Smith, Mahir Ibrahim, Francis Fitzwilliam, Lambeth Amara, Thaddea MacLeod, Anah Kahlo, and Archan Tate. The classmates all have different gifts and capabilities. Each has a patron, and Morrigan’s is Jupiter North.

Morrigan feels a nudge in a corner of her mind but can’t quite define it. She reflects on the purposes of the Wundrous Society, or Wunsoc: Publicly, it educates individuals with extraordinary talents, but secretly, it defends people against dangerous objects that previous Wundersmiths have left scattered around the city of Nevermoor.

Morrigan is a Wundersmith, a person with the capability to use and manipulate Wunder, a mysterious energy source that powers the realm. The previous Wundersmiths, of which there were nine at any given time, have been gone for 100 years, so it falls to the Wundrous Society to manage their creations. Their strategy is Containment and Distraction (C&D). Morrigan looks at the younger group, Unit 920, and part of her wishes she were still young and innocent. They have been warned, during the Parade, not to have any contact with the Unresting.

One week earlier, Morrigan’s class is lectured on the Unresting, ghosts driven by guilt. The goal of the Black Parade is to lure the Unresting away from the living. Only those holding a nightbeacon can see the Unresting, who will be relocated to a nonresidential area in the borough of Eldritch.

The parade begins on Hallowmas night. Morrigan’s patron, Jupiter North, carries a nightbeacon. As the procession continues, a group of protestors heckles Morrigan. Public opinion is against Wundersmiths since the last one murdered several people and tried to seize control of the city. Laurent St. James, leader of the hecklers and founder of the Concerned Citizens of Nevermoor, wants Morrigan to be sent back to the Wintersea Republic. When Jupiter confronts Laurent, he drops his nightbeacon. Morrigan picks it up and is horrified when she sees the Unresting gathered. She shouts at them, and the ghosts disperse.

Morrigan’s home, Room 85 at the Deucalion Hotel, can modify itself. For Morrigan’s sleepover with friends, it creates a giant treehouse with individual nests. Francis, a gastronomist whose foods can inspire emotions, brings a picnic. The classmates share ghost stories to amuse one another. Jupiter visits to ask if Morrigan is all right after her experience in the Black Parade, assuring her that the scattering of the Unresting was not her fault. Morrigan increasingly feels that there is something she is supposed to tell Jupiter. When everyone else is asleep, a rider on a horse made of smoke and shadow arrives at the door.

Morrigan meets Ezra Squall on the Gossamer, a conduit that allows Squall to move around in the form of energy and that allows them to meet unseen. They stand on a bridge over the River Juro. Squall wants to lift the Hush, the spell he put on Morrigan so that she doesn’t recall their meetings when they are apart. Morrigan isn’t ready to tell her friends that she is Ezra’s apprentice, given that he is the Wundersmith who murdered several people and was banished as a result. Ezra says that she needs to fix the problem she created by causing the Unresting to disperse at the Black Parade. When he accuses her of forgetting her lessons, Morrigan uses Wunder to create a wall of water that arches over their heads. He tests her on other lessons she has learned and tells her that she needs to practice. Then he tells her that they are going to visit the Guiltghast.

Squall takes Morrigan to the remote, empty harbor of Eldritch Moorings and explains that Hani Nakamura, a Wundersmith, created the Guiltghast. This is a large, squid-like creature that consumes guilt. The purpose of the Black Parade is to gather Unresting to feed it. Morrigan is uncomfortable with the idea “of feeding one monstrous thing to another” (62). She and Ezra quarrel, and Morrigan admits that she is worried the Guiltghast might try to feed on her because she is keeping her apprenticeship a secret. She returns to her treehouse room and forgets the events of the evening as the Hush descends again.

Holliday Wu, one of the public relations officials for the Wundrous Society, assigns civic engagement tasks for each student in Unit 919. She and Hawthorne’s patron, Nan, discuss entering Hawthorne in the Winter Trials, which is a competitive dragon riding event. Thaddea’s task is to teach self-defense to senior citizens. Lam is excused from public engagement because she is a member of a royal family who rules the Wintersea Republic state of Far East Sang. Anah, who wants to be a surgeon, will visit the Children’s Hospital posing as a healer. Morrigan is told she has important people to meet.

Miss Cheery, Morrigan’s teacher, joins Holliday and the stylist, Carlos, as they take Morrigan away. Holliday instructs Morrigan to say nothing about the Wundrous Arts where they are going. Holliday emphasizes that she wants to humanize Morrigan’s image so that people see her as more than just a Wundersmith.

Morrigan grew up in the Wintersea Republic, but Holliday reveals that a woman named Margot Darling has come forward claiming to be Morrigan’s aunt. She is of the Grand Old House of Darling from the Silver District, which means Morrigan is Silverborn.

Morrigan is astonished to learn that her mother was from Nevermoor. She, Holliday, Carlos, and Miss Cheery take the train and then a boat to a silver gate, where a man in a gondola shaped like a swan collects them. Morrigan brings Miss Cheery aboard with them in place of Carlos. Morrigan is impressed by how grand and elegant the Silver District is. When they reach a waterfall that is designed to keep out anyone uninvited, Morrigan uses Wunder to smuggle Miss Cheery through. She “imagine[s] reaching out through the Gossamer and then…she [can] feel it. Some extension of herself reaching far beyond her body” (90).

Darling House is serene and dignified, and Morrigan feels out of place. All she remembers of Meredith Crow is the face in her portrait; her mother died when Morrigan was born. Lady Darling, her grandmother, and her three aunts all resemble Morrigan’s mother. Margot tries to make Morrigan feel comfortable, but Morrigan senses that Lady Darling is distant and disapproving. Morrigan is hurt and angry that they never reached out to her before.

Desperate to escape, she invokes Wunder and shakes the floor, destroying the room. Morrigan thinks using Wunder feels “like finally stretching restless legs. Like scratching an itch or cracking her knuckles. Sheer, intense relief” (99). When Morrigan sees what she’s done, she wishes things could stop, and suddenly, the scene freezes. Morrigan realizes she’s performed Tempus, a Wundrous Art that she’s never been trained in. Ezra Squall appears on a Gossamer bridge.

When Ezra is near, the Hush lifts. He explains Morrigan’s actions by telling her, “Powerful feelings can forge powerful pathways into discovering our abilities” (103). Ezra knows Meredith Crow’s history: She was spoiled and rebellious, ran away from school, crossed the border to the Wintersea Republic to join the Wintersea Party, and married Corvus Crow. Morrigan realizes that means her mother was a traitor. She wants to confront Jupiter and ask why he never told her any of this, but Squall says that Jupiter has been summoned away. Morrigan feels exhilarated to know her mother’s history, which makes Meredith real to her. Morrigan asks if Squall can use Tempus to undo the destruction she caused to the reception room. He refuses, replying, “How will you find the courage to stand on your choices if I clean up every mess you make?” (107). Morrigan calls a shadow horse and rides it away.