The Cain family is thrown into disarray when teenage son Leopold is kidnapped. The family disagrees with how to handle the situation--should they call the police, or pay the ransom?
Conrad Cain reunites with his father to explore how his past may be related to Leopold's abduction. Meanwhile, the Cains learn that Leopold may not be the only one of their children targeted when the family receives a shocking package in the mail. Knapp sets off to Brown University to look for the Cain's eldest daughter, Aubrey, while advising Ellie and Conrad to keep up appearances as if nothing is wrong. Elsewhere, Agent Latimer King also picks up the trail at Brown University and is surprised to find out Knapp had beat him there.
Knapp and Special Agent Latimer King insist the Cains family keep up appearances and host their annual charity ball to prevent the public from discovering that Leopold has been kidnapped. Meanwhile, Conrad Cain confronts a former childhood friend who appears at the party unannounced. Elsewhere, both the private investigative team and FBI are on high alert as they wonder how he learned of the party -- and if he's the only one?
As Virgil is prepped for surgery Special Agent Latimer King realizes something is wrong, as the hired assassin -- "The Accountant" -- attempts to tie up loose ends by posing as a surgeon. Elsewhere Knapp goes undercover to investigate the specialized bullet that struck down Virgil. Meanwhile, Conrad Cain is interrogated by detectives regarding the murder of his childhood friend who was last seen leaving the Cains residence. Dana Delany tries to find comfort by joining an anonymous group for parents whose children have been abducted.
Knapp and Special Agent Latimer King sift through the burned-out remains of what was Schroeder Textiles and discover the room was carefully and expensively rigged to detonate on command. King and Agent Atkins soon learn the body found at the scene wasn't Schroeder and now armed with the suspect's real name - the agents join Knapp in a race to find the suspected mastermind. Elsewhere, Leopold struggles to reach the cell phone he lifted from the doctor before its battery dies.
Ellie Cain finds her father, Benjamin Rand, at the Cain's residence after being advised of the kidnapping of Leopold Cain. Rand seizes the case and makes a negotiation to get his grandson back that may cost him his life. Knapp and Special Agent Latimer King uncover some interesting information regarding the Cain family's past and possibly the location of Leopold. Meanwhile, Conrad Cain is arrested for murder of his childhood friend.
Knapp discovers that the Cain family was warned of Leopold Cain's possible kidnapping before it occurred. The FBI exposes a connection between Special Agent Latimer King and Virgil Hayes that is cause for suspicion. A woman comes forward with information that questions Conrad Cain's fidelity by revealing an affair he had with her daughter. Meanwhile, Conrad makes a public plea for his son's safe return, something that the kidnappers seem to be considering.
Turner exposes secret messages between Virgil Hayes and Leopold Cain, as Virgil unknowingly takes the law into his own hands to find Leopold. Elsewhere, the Mexican police question the kidnappers, forcing them to move locations. Meanwhile, Knapp tracks down Ellie Cain's mystery caller, and Conrad Cain attends the funeral of the man he is accused of killing, stirring up tension.
Virgil finds himself a wanted man, but Ellie still believes in him. Knapp and Turner interrogate the Accountant, while Conrad tries to find answers about what happened to Claire.
Knapp tracks down Gutman, but there is a contingency plan to release her that threatens the life of King's daughter. The Cains receive mail from various people who have heard of the kidnapping.
King looks into how the kidnappers transported Leo, Knapp finds information implicating Conrad in his own son's disappearance, Virgil asks Ellie for help in investigating Conrad's lawyer friend.
Bellows and Otto move Leo to an abandoned prison in preparation for the handover; Knapp, with Conrad, goes to Madeira, Mexico to pay the kidnappers for Leo's return; King follows the phone tip to Madeira, while directing Archer to look into who's framing him to look corrupt. Ellie continues to help Virgil, who also arrives in Madeira.
Leopold returns home, but King, Turner, and Knapp find the kidnapping's resolution to be incomplete; they continue to look into clues that remain unsolved.