The first chapter, "Little Seeds," describes the growing years of the main character, Patrick Lewis, providing causation for his subsequent actions in the novel. As a young boy in Depot Creek, Ontario, Patrick watches the loggers arrive in town in the winter, work in the mills in the other seasons, and skate on the frozen river. Patrick's father, Hazen Lewis becomes a dynamiter and is meticulous when washing his clothes each evening to remove remnants of explosives on his apparel. These elements form the foundation of the subsequent narrative: Depot Creek, the loggers skating, learning about dynamite, etc.
"The Bridge" deals with the construction of the Bloor Street Viaduct, which will link eastern Toronto with the center of the city and will carry traffic, water and electricity across the Don Valley. R.C. Harris, the city's Commissioner of Public Works often visits the bridge at night. One night, five nuns wander onto the unfinished bridge and one falls off. Nicholas Temelcoff, a Macedonian immigrant worker on the bridge, saves the nun who fell off the bridge, dislocating his arm. The nun, already missing her veil, tears her habit to make him a sling. Later, at a bar, he offers her brandy, compliments, and a new lease on life. Temelcoff is a silent man who struggles with English yet they are able to transcend their social and language barriers through the commonality of their scars— his from work, hers from being "always unlucky." This moment is the beginning of the nun's eventual transformation into the character Alice. He eventually falls asleep and wakes to find a doctor treating his arm and the nun gone.
As a young man, Patrick leaves the profession that killed his father and sets out to find the vanished millionaire Ambrose Small. This leads him to Small's mistress Clara Dickens, and to a relationship with her. Eventually, Patrick loses interest in finding Small, hoping only to remove Clara from Small. Clara tells Patrick that she will leave him to go after Small and warns him not to follow her. Patrick is broken-hearted. Three years later Clara's friend Alice unexpectedly arrives. Alice shows Patrick great tenderness and tells him that Clara's mother might know where Clara is. Patrick sets out to search for Clara. On meeting Clara's mother, Patrick learns that Clara and Small are living in his old hometown. Patrick finds Small living in a house owned by a timber company and Small attempts to set him on fire—once by dropping kerosene on him and then by throwing a Molotov cocktail. Patrick manages to escape to his hotel room and is visited by Clara, who dresses his wounds and makes love to him before returning to Small.
Palace of Purification
In 1930, Patrick is working as a dynamiter on a tunnel under Lake Ontario, a project of Commissioner Rowland Harris. Patrick rents an apartment in a Macedonian neighborhood. He is accepted into the neighborhood and is invited by Kosta, a fellow dynamiter, to a gathering at the Waterworks—a place where various nationalities gather for secret political discussions and entertainment. Patrick witnesses a performance in which an actor repeatedly smashes her hand against the stage and rushes forward to help her. He recognizes her as Alice Gull. His act of helping her turns out to be part of the show. Patrick visits Alice and learns about Hana, her nine-year-old daughter. Patrick and Alice become lovers. Patrick finds work in a leather company through Alice's friends and meets Nicholas Temelcoff, now a baker. On studying the bridge, Patrick learns about the nun that had fallen off, whose body was never found. He makes the connection after talking with Temelcoff and promises to look after Hana.
Patrick travels by train, north of Huntsville. He takes a steamer to a Muskoka hotel frequented by the rich, carrying nothing but a black suitcase. He burns down the hotel, then leaves on a small boat. Arriving at an island, he meets the blind Elizabeth. We learn that Alice has died and Patrick has committed the act of arson out of anger. Patrick swims out to a boat. He knows he will be caught by the authorities and takes the time to recuperate and dry out his clothes.
Three prisoners, Buck, Lewis and Caravaggio, are painting the roof of the Kingston Penitentiary. Patrick and Buck paint Caravaggio in the blue of the roof so he can hide and escape. He steals new clothes and changes his dressing. Jumping a milk train, he makes his way north toward cottage country. He has a scar from an attack from which Patrick saved him by yelling out a square dance call. Caravaggio recalls his first robbery, in the course of which he broke his ankle while retrieving a painting, so he had hidden in a mushroom factory where a young woman named Gianetta helped him recover, with whom he had escaped by dressing as a woman. Caravaggio enters the cottage of a woman whom he met on the lake and calls his wife to let her know he's all right. After talking to the cottage owner, he returns to his brother-in-law's house, reuniting with Gianetta.
Four years later, Patrick is released from prison and meets Temelcoff at the Geranium Bakery. Hana, now sixteen, has been living with Temelcoff's family. Patrick takes responsibility for Hana. One night, she wakes him to say that Clara Dickens has called. She tells him that Small is dead and asks him to pick her up from Marmora.
Realizing that the water supply is vulnerable to being cut off or poisoned, Harris installs guards at the Waterworks, which he built. Caravaggio introduces Patrick to his wife. They fraternize at a party for the rich, then steal a multi-million dollar yacht from a couple they chloroform. Patrick intends to blow up the Filtration Plant with dynamite and Caravaggio's help. Patrick enters the plant through the water intake. He places dynamite about the plant testing facility and carries the detonating box to Harris' office, where he accuses Harris of exploiting the workers and ignoring their plight. Patrick tells Harris how Alice Gull was killed and we learn that she accidentally picked up the wrong satchel, containing a bomb. Patrick exhausted, falls asleep, and in the morning Harris asks the police to defuse the bombs and bring a nurse for Patrick.
Patrick awakes and goes with Hana to retrieve Clara. At Hana's urging, Patrick tells her about Clara. Patrick asks Hana to drive to Marmora. The book ends with " 'Lights' he said"