One man's approximation of "water" with a Philadelphia accent, it's printed on a whiteboard during the premiere Tuesday of Discovery Channel's new mini-series Manhunt: Unabomber.

"When I say wudder, you learn everything about me," Jim "Fitz" Fitzgerald, the FBI profiler played by Sam Worthington (Hacksaw Ridge, Avatar), explains to a couple of his colleagues on the task force set up to catch the killer dubbed the Unabomber. "One tiny word, one tiny mistake, and you can tell I'm from Philly, blue-collar, local school, fan of [Flyers legend] Dave Schultz."

Clutching the 35,000-word manifesto that would eventually be tied to hermit and former college professor Ted Kaczynski (Paul Bettany), the agent asks: "What if there's a wudder … in here?"

"I say water now," the real James R. Fitzgerald said in a phone interview Thursday. But it was teasing about the agent from Olney's "pronunciation of H2O" while assigned to the San Francisco task force that set him on the path to finding the clues that tied Kaczynski to his words. That work was used to obtain the search warrant for Kaczynski's Montana cabin, leading to the arrest of the man whose bombs killed three people and injured 23 others between 1978 and 1995.

Unabomber's two-hour premiere of the eight-episode first season of what's envisioned as an anthology series  doesn't show us Bettany as Kaczynski  until the second hour. Much of creator Andrew Sodroski's script unfolds from Fitzgerald's point of view. So if all you remember of the Unabomber case is that Kaczynski was brought to the FBI's attention by his brother, David (Mark Duplass), you may be surprised by how much more there is to the story.

Not that there hasn't been some dramatic license, Fitzgerald said. When we meet Worthington's character,  for instance, it's some time after Kaczynski's arrest and Fitzgerald is living a life not unlike the reclusive bomber's, in a cabin far off the grid.

"I had some personal issues I was going through. Being away from my family was very difficult" while he worked the case, he said. But the retreat to the woods? Didn't happen.

"If anything, I went to the beach, to the Jersey Shore. But they chose the woods. It's emblematic, symbolic [of] some of the personal things I was going through at the time. But I didn't exactly mimic Ted Kaczynski," said Fitzgerald, who's a consulting producer on Unabomber.

As for the things that did happen, watching Worthington, an Australian actor who worked with a dialect coach to add Philly nuances to what Fitzgerald called "an excellent American accent," was "surrealistic," he said. "It's almost like you're looking into a window in the past. I was on the set when Sam was acting and saying some exact words I actually said back in '95 and '96."

Since retiring from the bureau in 2007 retirement from the bureau, Fitzgerald — who lives in Cape May County and consults as a forensic linguist — has learned plenty about the ways of television. He's served as a technical adviser on CBS's Criminal Minds and Fox's Sleepy Hollow, appeared as one of the experts last fall in CBS's The Case of: JonBenet Ramsey, and also did a show in Philly called Killer Profile for A&E, he said.

In Manhunt: Unabomber, "I'm really a composite character. I didn't do everything … that the mini-series presents. But anything to do with the language, that was me. That was my baby."

On or off TV, he's come a long way.

"My first job out of Penn State was 14 months as a store detective at Eighth and Market in the old Strawbridge's store," he said (as I typed away on the third floor of that very building, now a newsroom). "Some of my most dangerous capers occurred chasing shoplifters up and down Eighth Street."

They're not in Unabomber, but some of those capers found their way into A Journey to the Center of the Mind, Fitzgerald's planned four-volume memoir, whose third installment was published July 6. "Book One is growing up in Philly. Book Two is my 11 years as a Bensalem police officer [and] sergeant, and Book Three is the first 10 years of my FBI career, ending with a long chapter on the UNABOM case." (The case code name came from two Kaczynski bombing targets: universities and airlines.)

There's interest, he said, in a possible mini-series inspired by his Bensalem years, but he's not getting ahead of himself.

"I'm an Olney kid [who] found myself in the biggest investigation of the 20th century, at least the end of the 20th century. …  Now there's a mini-series being made about this? And my character's the protagonist?" he said.

"I sometimes I still wake up and pinch myself."

"Manhunt: Unabomber"
9 p.m. Tuesday, Discovery Channel.