Castle episode 5×06, “The Final Frontier,” finds Castle and Beckett at a Sci-fi convention trying to solve a murder while being pushed into the world of fandom, egotistical celebrities, and diehard costumed fans.

The episode is brimming with guest stars from all corners of the sci-fi universe. Ed Quinn (Eureka) is playing Gabriel Winters, the former star of the cult hit Nebula-9 who didn’t go on to have the best career since; Christina Moore (That ’70s Show) is Winters’ onetime costar, now a successful film actress; Chris McKenna (One Life to Live) plays a Nebula-9 superfan who may have been romantically involved with the murder victim; and Erin Way’s (Alphas) character was a business partner of the deceased’s. Jonathan Frakes (Star Trek: The Next Generation) is directing the episode. It will be interesting to see if there is any nod to Nathan Fillion’s beloved Firefly during the episode.

According to TVline, Castle will have its first ever Christmas themed episode on December 3. The episode will feature a ‘Kris Kringle’ as a murder victim who falls from the sky. As Castle and Beckett search for the killer they discover that this Santa may have been on the naughty list. The episode is entitled “Secret Santa” and will also show Beckett and Castle preparing for their first Christmas together.

[scrollGallery id=901 autoScroll=false thumbsdown=true]