Castle Episode 10 of "Castle" Season 7 will be Christmas-themed, featuring a killer dressed as Santa. Photo: ABC

It’s Christmas on the next “Castle.” While Castle (Nathan Fillion) and Beckett (Stana Katic) were brushing shoulders with movie stars in the last episode of Season 7 of the ABC series, in episode 10, the newlyweds will encounter someone even more famous than a movie star: Santa Claus. Unfortunately, the synopsis for the episode, titled “Bad Santa,” reveals that they will run into the Mafia as well.

According to the synopsis for the holiday episode, which premieres on Dec. 8, Castle and Beckett will be working on a case of an ER physician who was shot to death on the street. As they begin to investigate the murder, however, the case gets complicated when they discover that the dead man was a doctor for the Mafia and the murder had been a hit. Furthermore, Castle has a connection to the mob family that is behind the crime.

Watch the promo for episode 10 below.

The Christmas-themed episode will also be a tipping point in Esposito (Jon Huertas) and Lanie’s (Tamala Jones) relationship. The on-again, off-again couple was already shaken in episode 8, when Esposito was held hostage on a subway train by an armed gunman. Will Christmas finally inspire them to acknowledge their feelings for each other?

In a surprising twist, a picture from the episode (seen above) shows that the big red guy, or at least a guy in a Santa costume, will make an appearance as the murderer! Who or why, though, remains a mystery to fans.

What is Castle’s connection to the Mafia? Will Esposito and Lanie finally get together? Fans will have to tune in to find out. “Castle” airs Mondays at 10 p.m. EST on ABC.

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