"NCIS" Season 12, Episode 3 airs Tuesday, Oct. 7 on CBS. A Ziva David link opens in the new season premiere, then Tony DiNozzo is heard whining about being single in the next episode. This week, the focus is on Dr Ducky Mallard. There has been no confirmation yet that Cote de Pablo is returning even for a brief appearance in the show.

Spoiler alert: This feature contains minor spoilers on NCIS Season 12, Episode 3. Read at your own risk.

Sergei Michnev (portrayed by actor Alex Veadov) is the new big bad in the hit CBS drama NCIS. The Season 12 opener reveals this Russian character is a dear friend of Ari Haswari, half-brother of Ziva David (Cote de Pablo). Now Sergei wants to kill Gibbs to avenge Ari's death. Many fans are quick to speculate that Sergei is going to pull out Ziva David from wherever she is, in order to save Gibbs and his team.

NCIS showrunner Gary Glasberg has earlier hinted he is open to giving Tony and Ziva a moment to talk once again, as long as it would be organic to the story. With a man avenging Ari's death in the picture - and in the season premiere - fans find a big reason to speculate the said moment is happening this season.

In NCIS Season 12, Episode 2, Tony DiNozzo (Michael Weatherly) whines about being single. Spoilers reveal Tony is getting a new love interest this season, which makes many fans fear the Tiva days are really over. (On Twitter, there are speculations that Ziva David would return only to bid Tony a more final goodbye.)

This week, however, is all about Dr Ducky Mallard (David McCallum).

"Ducky returns to London after a case reveals a connection to his estranged childhood best friend. Agent Bishop accompanies him on the trip, and they interview his friend's family and coworkers. Meanwhile, Ducky recalls the choices he made in the past and the impact they've had on his adult life," reads the episode synopsis for NCIS Season 12, Episode 3, titled, "So It Goes."

Adam Campbell ("Mixology") is playing the role of young Ducky in NCIS 12x3. TV Line reported this episode will reveal why Ducky always wears bow ties.

NCIS Season 12 airs Tuesdays on CBS.