At the beginning of the novel, Theo is thirteen. He worships his mother, Audrey, who is also his best friend. Theo is fascinated by strangers and likes to keep secrets, which is the reason he follows Pippa and Welty in the museum rather than going with Audrey to the gift shop, a choice that likely saves his life. Theo is sensitive and insecure. Larry, Theo’s alcoholic father, has recently left home, which doesn’t bother Theo much. After Audrey’s death, Theo’s young psyche unravels. He starts making bad decisions out of shame, guilt, confusion, and an intense grief that he cannot express. When Theo moves to Las Vegas and meets Boris, he makes even worse choices and has little supervision. He and Boris enjoy a volatile friendship but form a deep, lifelong bond. Both boys’ mothers are dead. Both boys have abusive or neglectful fathers. And both boys simply long for unconditional love.

Back in New York, after Larry’s death, the adult Theo descends even further into despair, self-destructive behavior, and, finally, crime. He wants to heal from the grief and guilt from his mother’s death as well as the shame created when he took the painting. While in Amsterdam, he nearly kills himself after he fails to retrieve The Goldfinch. Only when the painting is returned to the art world does Theo find peace.