It was indeed an emotional midseason finale for "NCIS" when it featured Ducky's (David McCallum) story. It was a bittersweet ending with a big revelation on Ducky's past, but the show did not bring a cliffhanger episode. So what's next for the series?

The previous episode titled "Spinning Wheels" revealed that Ducky had a brother who is 20 years younger than him. This touching family-themed episode warmed the hearts of viewers as Ducky was finally reunited with his long lost brother in the end.

The episode then paves way to another family-themed story, involving a brother and sister.

"NCIS" season 13 will return in January next year and the series will feature a crossover special with "NCIS: New Orleans." It will be titled "Sister City" and will consist of two parts.

The episode will be featuring the crime-fighters from Washington DC and New Orleans, who will be working together to solve a case, as reported in CarterMatt.

Given that there will be a crossover of two shows and the suggestive title, the episode will give focus to Abby (Pauley Perrette) and her adopted brother, Luca (Tyler Ritter).

The news of Abby's brother appearing as a guest star was first reported by TV Line early in November.

In the first part of the episode, the Washington DC and New Orleans team will investigate the case of poisoned passengers aboard a plane.

Evidence gathered seems to implicate Luca who has gone missing and the team will need to find him to crack the case.

Meanwhile, the second part will feature Special Agent Pride (Scott Bakula) and the team continuing the investigation involving Abby's brother. Lab tech Sebastian Lund (Rob Kerkovich) will get a flight to D.C. to work with Abby on forensics.

With those synopses in place, the real question that viewers need answered is if Luca is really guilty of the crime.

They will just have to wait and find out when "NCIS" season 13 returns to CBS on Jan. 5, 2016.