On the season 12 premiere of the long-running US police drama "NCIS" to air on Tuesday, fans will find Agent Leroy Jethro Gibbs (Mark Harmon) and Agent Timothy McGee (Sean Murray) in Russia on a tricky mission for the agency, which means that their lives are already on the line as soon as the season starts.

The episode premiere entitled "Twenty Klicks" will focus on Gibbs and McGee's trip to Russia to make sure that one of the NCIS computer engineers linked to a classified intel in the US will land safety. However, their mission gets compromised, the two go missing, and they have to survive on their own. As if their situation is not complicated enough, a local mercenary group from Russia is also running after them.

Back in the US, Abby Sciuto (Pauley Perrette) is frantically worried about Gibbs and McGee, and even talks to NCIS Director Leon Vance (Rocky Carroll) for her team mates' safety.

CBS is silent about the reason for the gravity of this Russian mission, as well as the darker and more action-packed plot of season 12, but executive producer Gary Glasberg was willing to divulge several information with TV Fanatic.

"I think we came up with something that certainly is super action-packed and flips McGee and Gibss in an interesting, different scenario and we'll have to see where it leads throughout the season," he said.

Aside from the Russian mission, Agent Gibb's team will also have to deal with the entry of Ellie Bishop (Emily Wickerham) into their lives. In an interview with Digital Spy, Wickerham said, "You know, I know a little bit, there's a big collaboration over there and I'm excited to see where she goes, where they take her character."

"I hope she will meet her husband, know a little bit about her background," Wickerham added.

"NCIS" Season 12 premiere will air on Tuesday, Sept. 23 on CBS. Yet instead of the usual back-to-back premiere with "NCIS: Los Angeles," a new spin-off titled "NCIS: New Orleans" will be shown on the same date.

If you miss tonight's episode, be sure to catch it online via live stream on the CBS website.