TVLine gives us some hints about what's coming up on Castle.
Series creator Andrew Marlowe hedged when we asked about the next crucible on tap for crimesolvers-in-love Rick and Kate. "I don’t know.... Don’t we want to leave these two alone, so they can settle into their relationship? So they can get a groove?" he posed. "No. No. You want drama." Along those lines, on Jan. 7 you get the well-promoted return of Castle's ex-wife Meredith (who will crash at Rick's the same time Kate is doing so!) and a tricky first Valentine's Day featuring a "subtle competition" in gift-buying. The latter episode also features guest star Gina Torres, raising the question: Any in-jokes to be had for Firefly fans? "We’ll probably find something," Marlowe allows, "but I’m sure Nathan and Gina will find something as well." Elsewhere, an episode about an at-risk youth will reveal "a lot more of who Esposito is, what life was like for him growing up," and the return of big, bad Senator Bracken (Jack Coleman) will be met by "twists and turns" that add a new wrinkle to the Johanna Beckett mystery.
Source: TV Line