Our Missing Hearts is set in a near-future United States, where a recent economic collapse called the Crisis leads the government to pass legislation censoring “un-American” ideas. Though the named purpose of PACT (Preserving American Cultures and Traditions) is to protect the country from disunity and crisis by rooting out un-American ideologies, it instead leaves the nation in a dystopian state of surveillance and fear.
The novel begins when 12-year-old Bird receives a letter from his mother, Margaret, who abandoned him and his father three years prior for reasons he does not understand. The letter contains a drawing of numerous cats, but Bird does not know what the drawing means.
Bird and his friend, Sadie, used to bond over their missing mothers. Under the PACT law, authorities can take custody of children who are exposed to dangerous, unpatriotic ideas by their parents. Sadie was removed from her home and placed with a foster family because of her mother, Erika’s journalistic criticism of PACT. Last year, she ran away from her foster family, and Bird has not heard from her since.
Bird lives with his father, Ethan, who works in Harvard University’s library, though he used to be a professor of linguistics. At school, Bird is shunned for being the son of Margaret Miu, the seditious Chinese American poet. “Persons of Asian origin”—known as PAOs—are subject to greater surveillance and discrimination under PACT law, since the U.S. blames China for the Crisis. Bird’s memories of his mother center around the stories she told him, one of which was about a boy who drew cats. When he tries to research the story and his mother on a school computer, a teacher (Mrs. Pollard) warns him not to make trouble. Similarly, Ethan worries constantly about Bird being taken by PACT authorities. He reviews Bird’s social studies homework to ensure his son sounds appropriately patriotic, knowing that someone is always watching.
Recently, anti-PACT protesters across the country have been setting up art installations as a form of political resistance. On Harvard’s campus, trees are strung with red yarn and miniature knit dolls, which represent the children rehomed by PACT authorities. Often these displays refer to the children as “our missing hearts,” a phrase coined by Margaret and taken as proof of her un-American views. After a trip to Bird’s local library reveals that both The Boy Who Drew Cats and Our Missing Hearts (Margaret’s poetry collection) have been removed, he uses Ethan’s key card to sneak into Harvard’s library. Although Bird gets caught before finding any information, he finally remembers the story as Margaret told it to him.
In Margaret’s story, a boy draws cats on the walls of an abandoned house rumored to house a monster. While the boy sleeps in a cupboard, the cats come to life and kill the monster. This memory leads Bird to the house where he and his parents once lived. In a cubby in his old bedroom, he finds a New York City address in his mother’s handwriting. With the help of Carina, the Cambridge librarian who is covertly locating re-placed children, Bird takes a bus to New York. The address leads him to a townhouse on Park Avenue, where an intimidating woman he refers to as “the Duchess” (Domi) lives. She leads him to an abandoned brownstone, where Bird and Margaret reunite after three long years apart.
Margaret tells Bird the story of her life before his birth and why she decided to leave him and Ethan behind. While she talks, she uses tools to fashion strange devices whose purposes are unclear, using wires and bottle caps. In the evenings, she takes her finished creations out into the city, but she does not tell Bird what she is doing.
In her story, Margaret explains how she moved to New York for college. When the Crisis hit, unemployment rose, food and medicine ran short, and many businesses shut down. Margaret moved in with a fellow student named Domi, and the two of them worked as bike messengers. A few years into the Crisis, Margaret met Ethan and moved into his cushy apartment, cutting ties with Domi, who called her a sellout. Margaret began to write poetry for the first time since the Crisis began. Anti-Asian sentiment was rising as people blamed China for the economic collapse. Margaret’s mother and father were targeted and assaulted because of their Asian features, and they both died as a result. Margaret and Ethan moved to Cambridge, where Ethan worked as a professor. After Bird was born, Margaret published a book of poems she wrote about motherhood, entitled Our Missing Hearts.
PACT began removing children from their homes, provoking protests. At one march, a student named Marie Johnson was shot and killed by police while holding a homemade sign that read “ALL OUR MISSING HEARTS.” Marie’s death drew attention to Margaret’s poetry and her Chinese identity. Knowing that Bird would be taken by the authorities if she stayed, Margaret left her family and became a fugitive. After reuniting with Domi, who had by then inherited her father’s (Claude Duchess’s) tech company, Margaret traveled the country interviewing families whose children were removed because of PACT, recording their stories in notebooks.
This brings the story back to the present. Margaret only recently returned to New York to enact the final stage of her plan, which is still a secret to Bird. A librarian in Margaret’s network is harboring a re-placed child who ran away from her foster family, and it turns out to be Sadie. Sadie stays with Domi while Margaret reaches out to Bird, overwhelmed with guilt and longing for her son.
Margaret takes Bird with her to hide her remaining bottle caps throughout the city. Though Margaret almost abandons her plan because she does not want to put Bird at risk, Bird himself insists that doing nothing to stop injustice because it doesn’t directly affect her is hypocritical. The next day, Domi takes Bird and Sadie to her family’s isolated cabin to wait while Margaret sets her project in motion. In the city, Margaret uses a laptop and a microphone to connect to the devices in her hidden bottle caps. They are miniature speakers, designed with Domi’s help. For hours, Margaret reads the stories of the missing children from her notebooks, stopping everyday citizens in their tracks as they listen to the disembodied voice pouring from the city’s crevices. Margaret loses track of time, and the police find her location. Just before she is captured, she speaks directly to Bird, even though he cannot hear her, telling him she loves him.
Domi retrieves Ethan from Cambridge and brings him to the cabin, where Bird and Sadie are waiting. Bird knows that his mother’s actions will have a ripple effect despite her capture, and he feels he must make a choice between continuing to live in fear or standing up against PACT and oppression. The novel closes with Domi offering to rewrite one of Margaret’s lost poems she has memorized, which Bird gratefully accepts.