Sensing that the end was nigh, Major Crimes creator James Duff says, “I felt like I had to write a finale that would be worthy of the series, and worthy of the cast.”

But he also packed into the TNT drama’s 13-episode farewell run (launching tonight at 9/8c) an extra something extra, building up to its closer on Jan. 16, 2018.

“I gave Mary [McDonnell] something extraordinary to play, because she wanted to do something special,” Duff reveals. “She has been one of my partners throughout this process, so we decided on something interesting and different for her to play.”

Among the other series vets, “We increased the size of G.W. [Bailey]’s role [as Provenza],” Duff adds. “It is an interesting story that we’re telling [with Sharon], and Mary does an amazing job — her best work in the series is this season, and so is G.W.’s. A lot of the characters turn in spectacular performances.”

The bigger picture for Season 6 finds the MCD detectives “questioning their faith in the rapidly changing priorities of the justice system,” per TNT’s official synopsis. TVLine asked Duff to elaborate.

“I don’t wrote about politics,” he says, “but the political situation in the country is sopolarizing that it would be almost inauthentic to ignore it — especially around issues of immigration and ‘who is an American and who isn’t.’ Those questions affect law enforcement.

“The undocumented community in Los Angeles is a resource in fighting crime, notan impediment. Or at least that’s how the LAPD sees it,” he continues. “Trying to answer any issues related to immigration is beyond my ability — I wouldn’t know what to say — but I do know how the police officers feel about it, and I know how the FBI feels about it, and I know how certain Americans feel about it. So we do sort of take on that issue.”

Getting at the aforementioned “rapidly changing nature of the justice system” and how it specifically impacts police officers, “It is a big deal,” Duff maintains. “The LAPD and other local law enforcement organizations do not want to be tied up with finding undocumented people; they want to be taking violent offenders off the street. Gathering ‘illegal immigrants’ winds up being a paperwork morass, tying up patrol officers for hours. And the LAPD can’t afford to do it. So we talk about that.”

Asked to survey how the assorted MCD squad members weigh in on the hot topic, “The police never like change!” says Duff with a laugh. “But we do have people who are on the other side. And then we have someone who’s like, ‘It doesn’t matter what you think, it’s the law,’ and that’s the bottom line for many people. I try to represent everybody’s point of view.”

On a very separate note and in a storyline that is hinted at in the season opener (watch a sneak peek), Billy Burke’s Phillip Stroh — the serial killer and rapist who first terrorized Major Crimes‘ sire, The Closer — is set to resurface during the farewell run. Knowing that this was the final season, was it important for Duff to bring closure to that storyline, or was it simply time to revisit the recurring villain?

“I did not know it was the final season; I assumed it was,” he makes clear. “I didn’t feel like we were beyond the point of no return until Episode 6, and even then I didn’t want to say anything, because its not my job to. Plus, you’re always hoping for a reprieve of some kind. And we didn’t get one.”

But with Stroh again on the prowl and with McDonnell’s “extraordinary” storyline culminating, Duff promises no loess than “a big-ass finale” come mid-January. “You’re getting one that is surprising, funny, satisfying….” And maybe a bit of a tease.

“Since I didn’t actually know for sure it was the [series] finale, there is an open door…,” he admits. “It’s sort of a defiant ending, I would say, but an honest, truthful ending.”