The last time fans saw Sam (LL Cool J) and Callen (Chris O'Donnell), they were trapped inside a submarine filled with ammonium nitrate. In the season 6 premiere of "NCIS: LA," followers of the TV series will once again be sitting on the edge of their seats, as they watch what happens to the two special agents who are in for one very intense ride.

In an interview with TVLine, show creator Shane Brennan said, "It's a very, very intense opening episode, and at one point both Callen and Sam realize that in order to stop what they've discovered is a terrorist attack, they will have to, in fact, die. So it's pretty full on."

While the two are trying to keep the attack from happening, the situation is just as intense for the characters back at the headquarters. Granger (Miguel Ferrer) and Hetty (Linda Hunt) are trying to figure out how to stop the navy from taking action, or the two agents on board the sub will be "sacrificed." At the same time, Kensi (Daniela Rush) and Deeks (Eric Christian Olsen) are trying to unearth as much info and details as they can find.

Spoiler TV had posted a couple of pictures involving helicopters, suggesting that Kensi and Deeks will be doing an aerial search for the sub and their partners.

Also, for the initial three episodes, Hetty will be facing a senate inquiry where she will have to answer some really tough questions from the people higher up who are intent in finding out about the events in Afghanistan.

Meanwhile, the showrunner promises some "pretty full-on moment" between Kensi and Talia (Mercedes Masohn).

He said, "And what's great about it is there's a particular moment between Kensi and Talia that is resolved beautifully, in terms of the way the characters resolve their personal relationship and the way the two of them then have fun with Deeks."

"NCIS: LA" will premiere on Sept. 29, occupying a new Monday timeslot at 10 p.m. ET on CBS. If you miss tonight's premiere episode, be sure to watch it online via live stream on the CBS website.