Set in Montreal from the 1910s through the early years of World War II, the novel follows two orphans, Pierrot and Rose, whose intertwined lives trace a path from childhood love through separation, crime, and artistic ambition.
Pierrot is born in 1914 to a twelve-year-old girl at a Montreal hospital for unwed mothers. He appears stillborn but suddenly revives, and the nuns name him for his pale complexion and constant grin. Rose is born around the same time; her teenage mother pays a woman to place the infant with a wealthy family, but the woman abandons babies in the snow. Rose is found frozen in Mount Royal Park, barely alive. Both children grow up in an isolated orphanage on the northern edge of Montreal, where children are chronically underfed and beaten by nuns for trivial offenses.
The Mother Superior notices the two bonding as toddlers and orders them kept apart to prevent any attachment from forming. Despite the separation, both develop extraordinary gifts. Pierrot is a piano prodigy who plays by ear and delights the other children with absurdist physical comedy, from handstands to backflips. Rose entertains the girls' dormitory with elaborate performances featuring an imaginary bear who keeps proposing marriage, and she reads smuggled books in secret, earning harsher punishments than any other child.
When Pierrot is eleven, a young nun named Sister Eloïse arrives and begins sexually abusing him, framing the abuse as love. His personality shifts from buoyant to shadowed by deep sadness. One day, Rose holds his hand in the garden and tells him they will not be trapped forever, giving Pierrot his first glimpse of a future beyond the orphanage.
At a Christmas performance in 1927, when both are thirteen, Pierrot plays the piano onstage and Rose, lured by his music, wanders into view and begins an improvised dance as paper snowflakes fall. Their spontaneous act captivates the audience, and a wealthy patron pays the orphanage for the pair to perform in private parlors. They develop an intimate creative partnership. Rose conceives a plan for a grand revue she names the Snowflake Icicle Extravaganza.
Their bond is violently disrupted when Eloïse, who has escalated the abuse to intercourse, overhears Pierrot whispering sexual fantasies to Rose. Consumed by jealousy, Eloïse beats Rose so severely that she is hospitalized for weeks. Albert Irving, an elderly philanthropist, hears Pierrot playing through a window and arranges to adopt him. Pierrot writes Rose a farewell letter, but Eloïse intercepts and destroys it. Rose learns only that Pierrot has left without a word. He sends letters for three years; the nuns burn every one.
The two follow separate paths. Pierrot lives in Irving's mansion, absorbing aristocratic mannerisms and culture. When he visits the orphanage at eighteen, Eloïse lies, claiming Rose is married and repulsed by him. Irving dies, and his son burns the amended will, leaving Pierrot penniless. Poppy, a young prostitute, introduces him to heroin, and he quickly becomes addicted. He finds work as an usher and intermission pianist at the Savoy movie theater but spends his wages on drugs and begins stealing art from wealthy homes.
Rose is sent to work as a governess for the McMahon family in Westmount. McMahon, an imposing crime boss, runs nightclubs, heroin operations, and brothels. They begin a sexual relationship, and when his wife discovers the affair, McMahon installs Rose at the Darling Hotel as his mistress. He humiliates her when she asks for a role in his business and verbally abuses her to maintain control. On Christmas night, Rose leaves with her jewelry and moves to a cheap room at the Valentine Hotel. When her money runs low, she acts in pornographic films and befriends her costar Mimi, an intellectually brilliant woman. Rose delivers a stillborn baby with Mimi's help, then quits, determined to build her own show.
Both begin searching for each other. Pierrot spots Rose in a peep-show film and realizes Eloïse lied. He forces himself through withdrawal. Rose, on Mimi's recommendation, visits the Savoy, where the pianist plays a tune she recognizes as the one Pierrot composed for her in childhood. She waits outside, terrified. When Pierrot exits and sees her under the marquee, he calls her name. They fall into each other's arms. They confess their secrets, judge nothing, and move in together. They marry at City Hall with Mimi as witness, both twenty-two.
Happy poverty follows, but Rose delivers another stillborn baby alone in their room. Pierrot nearly relapses; Rose physically blocks him, and they survive the crisis together. Facing eviction, Pierrot retrieves a jewel-encrusted apple he stole years earlier and hid in a park tree, selling it to McMahon for twenty thousand dollars without knowing Rose's history with the crime boss. McMahon, realizing Pierrot's wife is Rose, is enraged. His men abduct Pierrot. McMahon forces Rose to smuggle heroin inside the show's papier-mâché moon in exchange for Pierrot's life, while secretly ordering Jimmy Bonaventura, head of the New York mob, to kill Rose after the delivery.
Rose recruits performers, secures an engagement at New York's New Amsterdam Theatre, and assembles the Snowflake Icicle Extravaganza. The troupe crosses the border by train, the heroin passing undetected through customs. The show opens to a rapturous audience. In the final act, Rose dances with her bear puppet while Pierrot plays his composition at the piano, both in white clown face paint as paper snowflakes drift down. The run is extended by a month.
Rose meets with Jimmy and maps out McMahon's criminal organization, proposing through implication that McMahon be killed. Jimmy agrees and gives her deeds to several Montreal buildings. But Pierrot, after visiting a children's hospital and reconnecting with his purpose of bringing joy to children, refuses to return to Montreal. He recognizes their enterprise as a criminal operation. When he presses Rose about McMahon, her silence confirms the assassination plan. He tells her she hates McMahon more than she loves him, and walks away.
Pierrot, believing Rose will never pursue her ambitions while tied to him, deliberately sleeps with another woman and uses heroin again. McMahon ensures photographs reach Rose. Devastated, she cancels the remaining shows, sleeps with Jimmy, and leads the troupe back to Montreal without Pierrot. McMahon is killed in his Westmount mansion.
Over three years, Rose transforms her buildings into thriving businesses. Her crown jewel, the Rose Theater, becomes the city's best venue. She never performs again. She refuses to run brothels, mentors women in difficult circumstances, and earns respect as a powerful businesswoman, though no one is truly close to her.
In New York, Rose sends Pierrot a suitcase of money. He spends it on heroin, then records his lifelong composition, selling the rights outright. The record,
The Ballad for the Moon, becomes a massive hit. Pierrot injects a fatal dose in a room at the Lonely Hearts Hotel. His final thought is a childhood memory of Rose, blindfolded, her hands reaching toward him. His funeral procession in Montreal draws hundreds; children place candles in their windows.
Months later, Sister Eloïse appears at Rose's office with a six-year-old boy named Isaac, Pierrot's son by Poppy. The child has blond hair, blue eyes, and a manner that recalls his father. Eloïse asks forgiveness; Rose grants it and takes the boy. As Eloïse walks away from the Valentine Hotel, a man follows and shoots her. Rose takes Isaac's hand, and together they leave to begin what the novel declares will be a wonderful childhood.