The "NCIS" cast -- Mark Harmon, Michael Weatherly, Sean Murray and Cote de Pablo -- spills secrets from the upcoming seventh season of the hit CBS series when they join Mary Hart on the ET stage.

"We've spent seven years getting this team together and that is in jeopardy," Mark tells Mary, referring to the season six finale. "The fact that both Michael and Cote are here -- and you're interviewing them -- should give our fans some hint about the predicament that Ziva [de Pablo] is in at the end of the first episode of season seven."

When "NCIS" returns with new episodes on Tuesday, Sept. 22, Tony DiNozzo (Weatherly) and Timothy McGee (Murray) are put in charge of finding a replacement for Ziva.

And on "NCIS," it is always a real possibility that cast members will be killed off. Special Agent Caitlin Todd (Sasha Alexander) was killed and replaced by Ziva, and NCIS Director Jenny Shephard (Lauren Holly) also met a deadly end.

"I was definitely a little worried," de Pablo tells Mary. "But also when I read the script, I thought, 'Well, this could be potentially really cool if they go in the direction that favors my character."

Ziva's absence means more for McGee than just searching for her replacement. Murray says, "McGee has to step up his game in terms of his responsibilities as an agent. Seeing the camaraderie between Tony and McGee getting all the stuff done, it's just growth."

So who would be the best investigator in real life?

"I think Mark Harmon without any questions is … he is sort of an investigator," Weatherly volunteers.

"I think it would be a mixture of Mark and Sean, because Sean is really into computers in real life and he's good at it," de Pablo says. "I just think Mark because he is wise."

The new season of "NCIS" debuts Tuesday, Sept. 22 at 8 p.m. on CBS.