Jackson Hunt, Castle's father, is back in episode 12 of "Castle" Season 6, Episode 12,"Deep Cover." The first time Castle met his father was when Alexis was kidnapped. The father had helped his son find his daughter. This time the father and son are meeting because of a murder investigation, and Castle's father, the former CIA agent, is a murder suspect.

The sneak-peek of "Deep Cover" shows Castle finding a laptop of the young victim who has been murdered. The laptop throws-up the name of Anderson Cross, the person who is running the Universal Banking Solutions' office at Manhattan. The victim had contacted the person.

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Castle and Beckett are at the office to question Mr Cross. Castle gets a call from his father, which is completely out of blue. Castle's father can be seen in the sneak-peek telling his son not to react, as something is about to happen. "Lives are at stake, don't react." Castle soon sees his father walk in as Anderson Cross, and is flummoxed. When Beckett is out of the hearing range, Castle can be seen saying in the sneak peek clip, "Dad!" Castle's father: "Not a word."

It looks like Castle's father will became the main murder suspect, as in the promo clip, Beckett accuses Castle of harbouring a fugitive. The episode's murder investigation is likely to put Castle in a dilemma. He will not be sure whether his father is a good or a bad man.

We wonder if Beckett will come to know in "Deep Cover" that Mr Cross is Castle's father. Castle has not told anyone that he had met his father when Alexis was kidnapped. It is time for Castle to let out his big, fat secret.

Official Synopsis of "Castle" Season 6 Episode 12, "Deep Cover': "The murder of a young video store clerk takes a strange turn when the team discovers his past history as a high-level hacker. But it's nothing compared to the shock Castle receives when their investigation leads them straight to his father, Jackson Hunt."