Plot
Even before her son Kevin was born, Eva Khatchadourian struggled with parenthood. As Kevin was a difficult child, she gave up her successful career as a writer in order to concentrate on raising him. Her son has developed sinister psychopathic traits, though his father, Franklin Plaskett, refuses to acknowledge the problem. As the situation turns catastrophic, Eva tries to figure out where she and Franklin went wrong.
In the wake of a school massacre committed by the 15-year-old Kevin, Eva begins writing letters to Franklin in November 2000. She reflects on her relationship with her husband and on Kevin's life. She also relates her current life: she was involved in both her son's criminal trial and a civil action against her (for parental negligence) brought by the mother of one of Kevin's victims. She sold the family home to pay for legal expenses, but in order to be near Claverack Juvenile Correctional Facility where Kevin is incarcerated, she still lives in the same town in which she remains shunned by the community. She regularly visits Kevin in prison, wherein they have a cold relationship.
Kevin seemingly regards everyone, especially his mother, with contempt, yet pretends to be manageable when Franklin is around. Eva perceives him as deliberately antagonistic, with his behavior ranging from petty sabotage to possibly encouraging a girl to gouge out her eczema-affected skin. Kevin resisted toilet training, which caused Eva to lash out and break his arm; Kevin told Franklin this was an accident and has since used the secret to manipulate her.
When Kevin is severely ill as a child, he briefly accepts Eva's care for the first time and rejects Franklin, seemingly too tired to put on an act of apathy. Kevin takes pleasure in learning archery after he recovers, yet seems otherwise unable to relate to human passion. As he grows older, he also takes an interest in manipulating his sycophantic friend Leonard, engaging in vandalism, and collecting computer viruses on floppy disks. He unsettles his peers, expresses disdain for convention by wearing uncomfortably undersized clothes, and follows news of school shooters and mass murderers. In high school, Kevin, Leonard, and two others accuse their drama teacher of sexual abuse; Eva is convinced he orchestrated the false accusations.
Franklin defends him, convinced that his son is normal and just misunderstood. Kevin plays the part of a loving, sensitive son whenever Franklin is around. Eva's apparent dislike for her son and the equal distrust between Eva and Kevin, as well as between Eva and Franklin, create a rift between the married couple. They have a second child, Celia, whom Franklin believes Eva favors. Kevin is aggressive towards Celia. When she is six years old, her pet elephant shrew disappears; the sink in the children's bathroom becomes clogged, which Eva clears with a caustic drain cleaner. While Kevin is babysitting Celia, she supposedly finds the cleaner and accidentally destroys her eye. Eva is certain that she put the cleaner away and that Kevin attacked Celia with it. This accusation leads Franklin to ask for a divorce, intending to take custody of Kevin; Kevin overhears them.
It is finally revealed that Franklin and Celia are dead. Kevin had killed them both at home with his crossbow before going to his school, where he trapped nine classmates, a cafeteria worker, and a teacher in a gymnasium and attacked them. Eva speculates that he did this because separation in the divorce would deny him a final victory over his mother, or to avoid being trapped in performing normality for Franklin. She believes he selected the people he chose for his victims because he resented them for having interests about which they were passionate. Kevin ensured himself a light sentence by timing the attack for three days before his 16th birthday in order to be charged as a minor, and used a prescription for Prozac to argue that he was experiencing violent psychotic episodes as a side effect.
The novel ends on the second anniversary of the massacre, shortly before Kevin will turn eighteen and be transferred to Sing Sing, a maximum security prison. Subdued and frightened, he gives Celia's prosthetic eye to Eva and apologizes. Eva asks Kevin for the first time why he committed the murders; he replies that he is no longer sure. They embrace, and Eva concludes that, despite what he did, she loves her son, and she awaits the day he is released so that she can welcome him home again.
