"NCIS" star MARK HARMON is on the ET set for a one-on-one chat with JANN CARL.

"NCIS" is wrapping up its fifth season on Tuesday, May 20, and it is the one show that consistently holds its ratings when programmed opposite FOX's powerhouse "American Idol."

"I know that the fan base is larger this year," Mark tells Jann. "We were locked in as a Top 10 show averaging 17 million viewers a week. It's nice that people have come to the show. We're proud of it of our hard work.

"I think people are continually finding this show," Mark continues. "People who give this show a chance stay with it and talk about it. The show's about characters, about comedy and there's a caper."

On tonight's penultimate episode, airing at 8 p.m. on CBS, Jimmy Palmer (BRIAN DIETZEN), Ducky's assistant, finds himself starring down the barrel of a gun after he witnesses a murder.

"He is the only one who can, not only finger the person who shot at him, but try to decipher from memory exactly what happened," Mark explains. "It's that moment that happens and you're asked to recall very small things that happened that most of us never think about. His mind is trained very differently because he's, basically, a doctor so it's an interesting show, it involves every cast member on the show passing through. Some think he's not going to ever find out who this guy is, or come to the conclusion of how we can find him. Then there are others that are totally supportive of him the whole time and think that he's going to come through and do this."