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

"NCIS" Season 12, Episode 12, titled "The Enemy Within," airs this Tuesday, Jan. 13, on CBS. This week's new episode picks up from a tragic event in NCIS 12x11. NCIS Special Agent Leroy Jethro Gibbs (Mark Harmon) and Senior FBI Agent Tobias Fornell (Joe Spano) gear up for a battle against Sergei Michnev (Alex Veadov) and his American ally. Meanwhile, viewers are reacting to the show's latest casualty.

Spoiler alert: This update contains "NCIS" Season 12 spoilers. Read at your own risk if you have not watched the previous episode.

In "NCIS" Season 12, Episode 11 ("Check"), Michnev shows Gibbs that his personal vendetta over the death of Ari Haswari has just begun. In this week's new episode, Veadov is not listed as a guest star, implying that the big villain's arc would not be concluded just yet.

"The NCIS team searches for a home-grown terrorist after a rescue mission in Syria reveals an American was involved in the capture of a social worker. Meanwhile, McGee and Bishop question DiNozzo's unusual behavior," reads the "NCIS" Season 12, Episode 12 synopsis on thefutoncritic.com.

Meanwhile, "NCIS" fans are sharing various reactions regarding the death of Diane (Melinda McGraw).

"I hated Gibb's pushy ex wife and I cheered loud and long when she was popped," says IBT AU reader Desert Dweller.

"Never expected Diane to get shot just like Kate did," says reader Sherry.

"Hated that they killed off Diane. She was the best thing to happen to that show in a long time!" Reader C Ellen writes.

Tony DiNozzo And Zoe Keates In NCIS Season 12, Episode 12

While hunting the American who is working with Sergei Michnev, McGee (Sean Murray) and Bishop (Emily Wickersham) find time to dig into Tony's (Michael Weatherly) dating status.

Marisol Nichols is reprising her role as ATF Special Agent Zoe Keates in this week's new episode. Rebecca, Gibbs' ex-wife no. 2 (Jeri Ryan) is also not listed as a guest star in NCIS 12x12.

"The Enemy Within" was written by George Schenck and Frank Cardea, and directed by James Whitmore, Jr.

"NCIS" Season 12 airs Tuesdays on CBS

Related TV Scoop and Spoilers

'NCIS' Season 12, Episode 11 Spoilers: Jeri Ryan Debuts As Gibbs' Ex-Wife No. 2, New Heartache And Crosshairs In CBS Teasers (Update)
'The Flash' Season 1, Episode 10 Update: One Reverse Flash Revealed, Captain Cold Returns With New Partner (Spoilers)