On the latest episode of "Castle," Castle's operative father was reintroduced during the search for a CIA mole. 

"Deep Cover" begins with a record store clerk's murder, who is killed under odd circumstances. It turns out the clerk was a genius hacker who may or may not have been helping catch a CIA mole.

The encryption on the victim's laptop is highly complex, but the date leads Castle (Nathan Fillion) to a person named Anderson Cross, and his company of multimillion dollar money transfers.

It turns out that Cross is actually Jackson Hunt (James Brolin), Castle's dad, who has been tasked with finding the mole. The hacker learned the identity of the mole, but was murdered before he could tell anyone. Although Castle is shocked to see his father again, he wants to meet with him.

Hunt is then shot while trying to catch the mole, so Castle and Martha (Susan Sullivan) have to perform surgery in the kitchen.

More complications arise when Beckett (Stana Katic) comes over and is told the story. Hunt then says that he has to go a place where the mole, Gemini, is uploading the CIA's list of deep cover operatives. Due to his injury, Castle volunteers to go instead. The plan goes sour when Gemini appears and kidnaps Castle at gunpoint. Hunt shows up in the nick of time and is able to rescue his son and kill Gemini.

Beckett appears just as Hunt leaves with the body, and proceeds to comfort Castle.

Castle reaffirms that she is his family now. Then, after a lot of deliberation, the two finally set a wedding date for September.

On the next "Castle," the case-of-the-week will focus on the death of a young pop star.

In the next episode, called "Limelight," "When a rising young pop star is found dead in an alley, Castle and Beckett are going to delve into the victim's out-of-control hard-partying lifestyle. However, as they dig deeper, a shocking revelation will threaten to rock their investigation. Alexandra Chando ("The Lying Game," "As the World Turns") will guest star in the episode as Mandy Sutton."

The death of the pop star will remind Beckett that she is marrying someone who is in the public eye.

"What happens when stories about him appear in the press that aren't true? How does she feel?" executive producer Andrew Marlowe told TVGuide. "She's kind of private person."

Watch the promo for "Limelight" below, which airs Mon., Jan. 20 at 9 p.m. on ABC.