Rocky Carroll by Cliff Lipson/CBS Rocky Carroll by Cliff Lipson/CBS

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Leroy Jethro Gibbs is investigating the murder of a serviceman in a grimy trailer park, quizzing the dead man's landlady and dispatching his team to take photos and do background checks. The setting is a hot summer day in Newhall, 40 minutes north of Los Angeles, and the talk is vintage NCIS: sifting through clues, making connections, dropping in the occasional wisecrack.

But things are off-kilter in a way that has nothing to do with Gibbs ( Mark Harmon) or the case. It's the people surrounding him who don't seem right. Instead of his longtime team of Agents DiNozzo, McGee and David (Michael Weatherly, Sean Murray and Cote de Pablo), Gibbs is working with a group of new faces played by Liza Lapira, Jonathan LaPaglia and Jonathan Mangum.

The shocking change happened in the closing minutes of last season's finale, when, following the murder of director Shepard (Lauren Holly), new NCIS director Leon Vance ( Rocky Carroll) disassembled the team. He assigned McGee to cyber crimes and DiNozzo to the USS Ronald Reagan and terminated David's position, sending her back to Israel.

The result, says executive producer Shane Brennan, has shaken up a show that earned its best ratings ever in its fifth season. "To look toward Ziva's desk and see somebody else there has been very disconcerting to all of us," he says. "But it's been a fun ride, it really has."

Fun? That's probably not the word Harmon would use. "Shooting this episode is hard," he says during a break on the set. "The one constant is Gibbs - but it's odd for him, and it's odd for the guy playing him."

Brennan promises "a season of surprises," including revelations about exactly why Vance broke up the team. "Who is this guy Vance?" he asks. "Is he a good guy or a bad guy? We promised fans a rollercoaster ride, and they're gonna get it!"

As for the old team, not to worry - they haven't gone AWOL. "It's taken a long time to get this group together and to be as successful as this show is" Harmon says, before adding with a grin, "I mean, we're in Year 6 and there's more talk about NCIS now than before. So you've got to give someone credit for doing something right!" - Steve Pond