Hunt

Concluding the two-part story, Castle becomes frustrated with the search for Alexis when the FBI and NYPD are slowed down by bureaucracy. Taking matters into his own hands, he decides to go after Alexis himself. As he ventures into the criminal underworld alone, Beckett realizes that Alexis was the target of the kidnapping to begin with, but is too late to stop Castle from blindly wandering into an ambush. He is saved by a mysterious stranger, a spy calling himself Jackson Hunt (James Brolin), and who reveals himself to be Castle's father. Alexis' kidnapping has been orchestrated by a Russian named Volkov to force Hunt into showing himself so that Volkov can kill him in revenge for the death of Volkov's wife. Having tracked Alexis to Paris but knowing that he could not stop Volkov alone, Hunt brings Castle in and together they confront Volkov to barter for Alexis' life.