Actress Stana Katic poses at the 2014 Environmental Media Awards at Warner Bros. Studios in Burbank, California
IN PHOTO: Actress Stana Katic poses at the 2014 Environmental Media Awards at Warner Bros. Studios in Burbank, California October 18, 2014. Reuters/Mario Anzuoni

On Monday night, "Castle" Season 7 will be airing its mid-season finale. The episode 10, which is titled "Bad Santa," will see Rick Castle knocking at the doors of a mobster, seeking his help to solve the murder of a mob doctor. The famous writer and the husband to homicide detective Kate Beckett is set to become an "honorary mobster." Also in this mid-season finale, Lanie and Esposito's on and off relationship will see a defining moment.

For Castle, it is going to be a "very mobster Christmas" in "Bad Santa." Entertainment Weekly is reporting that Castle will get involved in a "potential mob war" and also due to an "unexpected blood oath," he will be becoming an "honorary mobster." Beckett's reaction is going to be worth watching.

The episode 10 will also see movement in Lanie and Esposito's relationship. The last episode of "Castle" Season 7 saw Esposito being held as a hostage, along with other passengers, in a car of the subway. After his brush with death, "Esposito is going to reflect on his relationship with Lanie, and consider its importance in his life," David Amann, showrunner of "Castle," said to TV Guide.

"Castle" Season 7 introduced a new mythology revolving around Castle. There have been no major revelations related to that till now. And, the mid-season finale is unlikely to explore that storyline. According to TV Guide, it is in February that Castle's disappearance mystery may get picked up. "Bad Santa" is a Christmas episode and it "has a bit of a lighter touch...right up until the end," TV Guide reports. Amann has hinted that they are looking at a "game changer for Castle" at the end of the episode.

According to the official synopsis of "Castle" Season 7 Episode 10 "Bad Santa": "When an ER physician is gunned down in the street, Castle and Beckett soon discover that the victim was a mob doctor to a Mafia family run by an old friend of Castle's. Also, against this backdrop of Christmas, Esposito and Lanie reach a defining moment in their relationship."

[Youtube: Television Promos]