Theodore “Theo” Decker and his mother visit New York City’s Metropolitan Museum of Art so she can view the masterpiece The Goldfinch. While they are at the museum, a bomb explodes, killing Theo’s mother and traumatizing him. During the immediate aftermath, Theo meets an old man who is dying from his wounds; the man presses a ring into Theo’s hand and tells him the name of a business establishment. Theo, bleary from the trauma, grabs The Goldfinch during the bombing mayhem and takes it home with him.
Because Theo’s father is absent from his life, Theo goes to live with the Barbours, his classmate Andy’s family. He finds the business the dying man with the ring told him about; the business sells and restores antique furniture. Theo befriends the owner, Hobie, who was business partners with the deceased man, Welty. Hobie looks after Welty’s niece, Pippa, who was also at the museum when the explosion occurred and now suffers from trauma and physical injuries. Theo falls in love with Pippa, but she is sent to live with blood relatives. They see each other when Pippa infrequently visits Hobie in New York City.
Theo’s father resurfaces just as the Barbours are set to adopt Theo. Theo moves to Las Vegas with his father and his father’s girlfriend, Xandra. There, he becomes close friends with Boris, a Russian immigrant with vaguely similar circumstances to Theo’s. This entire time, Theo has smuggled, hidden, and coveted The Goldfinch. For Theo, who is unsure of what to do with the painting or even how to return it, the artwork becomes a touchstone to his mother and a source of comfort, as well as an ever-present conundrum.
Theo and Boris spend their days drinking and experimenting with drugs, trying to numb themselves to the neglect and loneliness in their lives. Both are children of alcoholics, and Boris is often beaten severely by his father. Theo’s father has a mysterious source of income that, although never completely revealed, appears to involve gambling. A mysterious man begins arriving at Theo’s house and asking for Theo’s father. Soon after, Theo’s father demands that Theo call his mother’s lawyer to ask that a large sum of money from Theo’s trust fund be transferred into Theo’s Las Vegas financial account. Unaware that a trust fund was set up for him, Theo obeys, but the lawyer denies Theo’s request. Shortly after, Theo’s father is killed in a car accident, which may or may not have been intentional.
Realizing that he is alone in the world and fearing placement in foster care, Theo steals money and drugs from Xandra, takes her neglected dog, and boards a bus to New York City. He wanders the city streets and eventually arrives at Hobie’s doorstep; Hobie takes him in willingly. Theo learns the antiques trade and eventually becomes a business partner, all the while functioning as a drug addict. Unbeknownst to Hobie, Theo creates a business scam to sell restored antiques as valuable originals.
The painting remains in Theo’s possession, carefully sealed in layers of material and duct tape that Theo never unwraps. He reads about a group of people who, during the confusion of the museum bombing, stole artwork and have now been arrested for trying to sell them. Out of concern for himself, Hobie, and Pippa, Theo rents a storage locker and hides the painting there. Lucius Reeve, one of the victims of Theo’s business scam, confronts Theo with the idea that Theo possesses The Goldfinch and is using it for criminal purposes. Theo dismisses Reeve and his claims.
Theo learns that Andy Barbour and his father drowned while sailing. Shocked by these deaths, Theo reconnects with the family and begins to date Kitsey, Andy’s younger sister. Eventually, Theo and Kitsey become engaged despite the fact that he is still very much in love with Pippa. He discovers that Kitsey is also in love with someone else, but they decide to remain together in an unpassionate relationship.
Theo runs into Boris on the street. Boris is now very wealthy from associating with an underground network of mysterious individuals. Theo learns that Boris stole The Goldfinch from Theo back in Las Vegas and has been using it as collateral for his criminal dealings since then. Shocked, Theo goes to the storage unit and unwraps the “painting” only to find it contains a high school textbook. Boris is relatively sorry, especially because someone else now has the painting since he used it as collateral. However, Boris hatches a plan to reclaim the painting for Theo.
Theo and Boris travel to Amsterdam to reclaim the painting. During a chaotic and frantic series of events that include a shootout, Theo shoots and kills a man. Boris is shot in the shoulder, but the two manage to escape. Boris tells Theo to wait at the Amsterdam hotel where Theo has been staying. Theo remains there for weeks, surviving on room service and heroin. He doesn’t have his passport, and having committed murder, he is afraid to leave his room. He decides to commit suicide, but before he can, Boris reappears.
Boris hands Theo a great deal of money and tells him that it is his share of the reward for the return of the painting; Boris managed to have the painting returned to the authorities. Theo returns to New York City, where Hobie confronts him with details of his business scam, which Lucius Reeve revealed to Hobie. Theo divulges everything to Hobie, and they decide to buy back the fake antiques in order to restore the business’ reputation and honor.
Theo’s life and relationships are generally left open-ended at the novel’s close. Pippa assures Theo that she loves him but will never be romantically involved with him. Kitsey and her family invite him to be a part of their lives, whenever and however he chooses. And Hobie remains a close companion as Theo begins to travel the world alone, finding solace in not being anywhere.