"Castle" Season 6 returns on Monday, 21 April, with episode 20 titled "That 70s Show." The gang of "Castle" experience the New York of 1970s when they discover the body of a New York mobster who had disappeared in the seventies.

The witness of the episode is stuck in the disco era, as he thinks it is still in the seventies, according to the synopsis of the episode. To make him cough out the information, Castle and Beckett play along with his delusion. The episode features them dressed-up in the style of the 1970s.

TV Guide's Mega Buzz reveals that this episode is "more grounded in reality," as Beckett finds that the witness has a sexist view against women. He does not seem to see women as equals. This will make Castle take the lead in this mobster murder investigation.

"Unfortunately for Beckett, the witness shares Archie Bunker's views on women, which forces Castle to take the lead on the case -- and in turning back the clock on the 12th Precinct," according to TV Guide's report.

Meanwhile, Lanie is set to appear in Foxy Brown get-up in the episode. Esposito's reaction to Lanie's appearance will be worth watching, according to TV Guide.

Talking about this episode, Andrew Marlow, creator of "Castle," has said to Give Me My Remote in an interview that it is a "really, really fun episode that takes us into the world of the 1970s, into the middle of the disco era. It's a different device than "Blue Butterfly," that allows us to see our characters in that era. So that's going to be fun."

"Law & Boarder" is the title of episode 21, which is scheduled to air on April 28, 2014. This episode features the murder investigation of a promising skateboarder. A mysterious motorcyclist guns him down. According to the synopsis of this episode, this murder investigation will thrust "Castle and Beckett into the world of extreme sports, where the death defying stunts aren't the only thing that's dangerous."