Rick may have been found — and, in fact, he has been working on cases during the first half of season 7 already — but there's still not much information about what happened to him and why he has amnesia. The upcoming episode will finally tackle this mystery. 

According to TV Line, a returning cast member will join in solving the mystery behind Rick's amnesia. She is none other than Annie Wersching ("24") and she will reprise her role as Dr. Kelly Nieman. 

Wersching teased the show's fans on Twitter with a photo on set with Nathan Fillion (Rick Castle). But the latest photo shows her name tag on her doctor's coat, which pretty much confirms that she is returning this season.

The photo was captioned: "Dr. Nieman is back at it! This means she's legit right?"

She is as legit as can be. 

But Dr. Kelly Neiman's return isn't just to help out Rick with his memory loss. Apparently, the doctor is also linked to the 3XK story arc, which may finally be wrapped up in the upcoming episode. According to Carter Matt, it will be good to finally end the story arc here since there's still a lot of important questions that need to be answered in the remainder of the show. There's still the mystery behind Rick's disappearance. 

The return of Neiman is something that fans do not mind at all. She is one of those likeable characters that viewers would like to see as well. Carter Matt described her as both "intelligent" and "shrewd." She is intimidating, too.

Moreover, episode 12 will also be about Rick Castle going into the telenovela world. Kamar de los Reyes will guest star. It will be interesting to see what Reyes' character will be. 

"Castle" season 7 episode 12 is set to air Jan. 19. It will be a two-part episode.