CBS’ Naval Criminal Investigative Service is heading Down Under for its first international edition.

“NCIS: Sydney,” premiering Tuesday (8 EST/PST and streaming on Paramount+), is the fourth spinoff of last season’s most popular scripted broadcast series. It follows stateside versions based in Los Angeles (2009-23), New Orleans (2014-21) and Hawaii, which debuted in 2021. Though initially intended only for Australian viewers, the CBS-produced series was picked up to help fill a schedule affected by writers and actors strikes, both resolved as of last week.

“You've got the world's largest (natural) harbor, and (a continent) in the most contested patch of water on the planet,” says “Sydney” creator Morgan O'Neill. “It's astonishing that ‘NCIS: Sydney’ doesn't already exist. It's a really fertile ground for telling the type of stories that the ‘NCIS’ franchise tells.”

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'NCIS: Sydney' upside-down commercials

The network had some fun with NFL viewers Sunday, airing promos for "Sydney" that were upside down, playing off the the continent being known as "Down Under." Some questioned on X, formerly Twitter, whether the commercial aired upside for everyone. Others were split as to whether the stunt was "great marketing" or nausea-inducing and "annoying."

Main 'Sydney' characters 'lock horns' during premiere

The Royal Australian Navy granted access to film on its bases, ships and helicopters, O'Neill says. The executive producer also spoke to actual members of the Naval Criminal Investigative Service, the agency that probes crimes involving members of the U.S. Navy and Marine Corps, to understand how they partner with Australian authorities.

“We worked out how they interact, which is basically to work under the umbrella of Australian law enforcement jurisdictions,” says O'Neill. “In the case of ‘NCIS: Sydney,’ they function under the umbrella of the Australian Federal Police, which is the Australian equivalent of the FBI.”

But in the TV version, the collaboration doesn’t always run smoothly. NCIS special agent Michelle Mackey (Olivia Swann), taking the lead on an investigation into the death of a petty officer assigned to a U.S. nuclear submarine, results in a power struggle with AFP Sergeant Jim “JD” Dempsey (Todd Lasance).

“They lock horns at the beginning, and that's part of the fun,” O'Neill says. “I suppose by the end of the pilot, the question will be asked ‘Are these guys a good fit? Will they ever be a good fit? Will this hot-headed maverick (and) former Marine Corps chopper pilot ever be able to have a functional relationship with this laid-back Australian larrikin, country AFP sergeant?’”

The close-to-the-vest Mackey reminds O'Neill of Leroy Jethro Gibbs, the role played by Mark Harmon from the original series 2003 debut until his October 2021 exit.

She carries memories of Iraq and Afghanistan "in a way that is quiet and dignified, but conflicted and troubled and sometimes difficult to tap into and difficult to express,” says O'Neill. “She's also unconventional, and I think that's what makes her such a good investigator. She doesn't really take the expected pathway, and that rubs a lot of people up the wrong way who like things just so.”

Dempsey’s former career as a teacher helps him detect deceit, a talent “honed from years of 15-year-olds lying to him about why their homework wasn't done,” O'Neill says. “He actually parlays that into an ability to interrogate suspects and to put the pieces of the puzzle together in ways that are really, really compelling.”

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Who's in the 'NCIS: Sydney' cast?

The cast is rounded out by NCIS special agent DeShawn Jackson (Sean Sagar), whom O'Neill likens to an American Paddington Bear as he’s “endlessly curious”; AFP constable Evie Cooper (Tuuli Narkle) who has a “street sass about her”; dry-witted AFP forensic pathologist Roy Penrose (William McInnes) and green whiz-kid AFP forensic scientist Bluebird “Blue” Gleeson (Mavournee Hazel).

Viewers might also see familiar faces from the “NCIS” universe if there are future seasons of “Sydney.” O'Neill says appearances by stars from other locations have been discussed.

“We're hopeful that we can lure and entice some of the stars of the other franchises to take the very short flight down to Sydney and come out to the harbor and solve a few crimes with us,” he jokes. “There's certainly huge opportunity for that, and we'd be mad not to try and maximize that. That's definitely in our future.”

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