| Director | Gavin O'Connor |
|---|---|
| Budget | $44 million |
| Box office | $155.2 million |
An autistic child whose mother desires to have him treated at the Harbor Neuroscience facility is instead raised by his father, a U.S. Army psychological operations officer who refuses to enroll him. When the mother leaves the family, unable to cope, the father trains him and his brother in martial arts, encouraging the child to acclimate himself to triggering stimuli rather than avoiding them.
As an adult, the child is known by the alias Christian Wolff and acts as a forensic accountant investigating criminal organizations, "un-cooking" their financial records to uncover thefts. He operates a small accounting office in Plainfield, Illinois, that serves as a front for his money laundering enterprise. He assists a farmer and his wife with their tax problems, and is seen living a regimented life in a suburban property. His criminal clients contact him via an unnamed woman (later revealed to be Justine, daughter of Harbor Neuroscience's founder), who also organizes his business, identities and life using a computer-generated voice over the phone. After Living Robotics' CEO, Lamar Blackburn, and his sister Rita learn of accounting irregularities from in-house accountant Dana Cummings, they hire Christian to audit their firm with Dana's assistance.
Christian informs Rita he's discovered $61 million has been embezzled but doesn't know the thief's identity. That night, Living Robotics CFO Ed Chilton is forced by a hitman to overdose on his insulin. Lamar pays Christian his remaining fee and tells him to leave. Christian kills two hitmen who attempt to kill him. Learning from one that Dana has also been targeted, he prevents another team from killing her in her apartment, then takes her to his storage unit, which contains an Airstream recreational vehicle filled with artwork and valuables he's accumulated by purchase or as payment for previous jobs. He hides Dana at a hotel and goes to confront Rita, finding her murdered. He suspects Lamar is her killer.
Treasury Director Ray King is blackmailing data analyst Marybeth Medina, who omitted her juvenile criminal record from her federal employment application, to get her to find a shadowy figure known as "The Accountant". Medina realizes Christian is using the names of great mathematicians as aliases and tracks the Wolff identity to the accountancy office and adjacent businesses used to launder money. King, Medina, and a group of agents search Christian's home and King tells Medina that Christian was incarcerated following a violent altercation at his mother's funeral which resulted in his father's death. In prison, Christian formed a bond with Francis Silverberg, a former accountant turned informant, linked to the Gambino mafia family.
King, who was working Silverberg's case, is skeptical of Silverberg's claims. King had facilitated Silverberg's release, inadvertently leaving him vulnerable, and was consumed by guilt when the Gambino family murdered Silverberg, torturing him to death. King sought to make amends by surveilling the Gambino family, and thus witnessed Christian eliminating the entire Gambino family in revenge. Christian overpowered King and spared his life after King expressed remorse for his role in Silverberg's demise and shared his pride in being a good father. Following this encounter, Christian vanished but continued to provide King with tips into various criminal activities, allowing him to have a successful career.
Medina determines that Christian adheres to a set of moral principles. King proposes that she take over his role upon his retirement, which is imminent, and continue to accept information from Christian. She declines, unable to rationalize receiving tips from a murderer. A phone call interrupts their conversation: Christian's partner has called the phone in the vacant house to provide him with a lead regarding Living Robotics.
Christian goes to Lamar's mansion and fights through the waiting team of mercenaries protecting Lamar, during which he is injured. Braxton soon recognized Wolff as his brother upon Wolff chanting the Solomon Grundy rhyme. They fight, Braxton blaming Christian for their father's death, but reconcile and Christian kills Lamar. He promises to meet with Braxton before he leaves.
Another set of parents visit Harbor Neuroscience. They meet Justine, the daughter of the clinic's director, who is revealed to be Christian's business partner. Medina accepts her new role as Christian's contact and speaks at a press conference on the Treasury's investigation into Living Robotics.
Dana receives a framed copy of Dogs Playing Poker but discovers an original Jackson Pollock painting from Christian's Airstream hidden underneath it. In the final scene, Christian is shown driving on a country road with his Airstream in tow.