Michael Weatherly
NCIS actor Michael Weatherly has been arrested for DUI. Here, he arrives at the 2014 People's Choice Awards in Los Angeles, California January 8, 2014. Reuters

In this week's episode of "NCIS" Season 12, Leroy Jethro Gibbs (Mark Harmon) loses another dear friend after being mercilessly pulled back into some of the biggest deaths the series has ever shown. The next episode launches Gibbs and Fornell on a hunt to make "the enemy within" pay for the season's biggest tragedy so far. Meanwhile, Tony DiNozzo (Michael Weatherly) is keeping the romance alive in his life.

Spoiler alert: This update contains NCIS Season 12 spoilers. Read the quick recap at your own risk if you have not watched Episode 11.

To quickly recap, when NCIS Season 12, Episode 11 ("Check") begins, Gibbs has two ex-wives linked to the latest NCIS case: Diane (Melinda McGraw) and Rebecca (Jeri Ryan). A few minutes before the episode ends, one of them dies the way Agent Kate Todd (Sasha Alexander) dies in the Season 2 finale.

Sergei Michnev (Alex Veadov) goes into a killing spree to avenge the death of Ari Haswari (Rudolf Martin), his "family." First, he copies the crime scene in the death of Jenny Shepard (Lauren Holly). Then he kills someone in the same manner Mike Franks (Muse Watson) was killed. Finally, for his it-comes-in-threes attack: Diane dies with a sniper shot to her head.

FBI Agent Tobias Fornell (Joe Spano) is appearing in NCIS Season 12, Episode 12 ("The Enemy Within") to join Gibbs and his team in hunting down Michnev. It is revealed in NCIS 12x11 that a man with American features is part of Michnev's crew.

Meanwhile, ATF Agent Zoe Keates (Marisol Nichols) resurfaces in NCIS 12x12. In the CBS promo clip, it is hinted that Tony and Zoe are doing well together, and the team is beginning to notice. At least one of them goes to as far as saying: "Tony's in-love!"

In the NCIS Season 12, Episode 12 promo clip, it's Abby (Pauley Perrette) who finds out from evidence that "there was another American working with the terrorist." The clip quickly segues to NCIS Director Leon Vance (Rocky Carroll) telling a crowd to quickly get out of a building.

NCIS Season 12, Episode 11 was written by Steven D. Binder and directed by Alrick Riley.

NCIS Season 12 airs Tuesdays on CBS.

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