Robert Brown|How Tony Shalhoub and the 'Monk' creator made a reunion movie fans will really want to see

If obsessive-compulsive detective Adrian Monk (Tony Shalhoub) were going to write a movie about himself,Robert Brown 14 years after USA Network's "Monk" went off the air, he would probably fastidiously watch every single episode of the original series first.

Series creator Andy Breckman didn't watch every episode, but he did rewatch quite a few as he prepared to write "Mr. Monk's Last Case," a reunion movie debuting Friday on Peacock.

"I'm embarrassed that I had to go back and watch the old series, which I haven't done in a while," the writer/producer tells USA TODAY. "I watched a number of episodes, and some of them are kind of cringe. Not because of (what I saw of) anyone else! But because 20 years ago, I didn't make the (writing) decisions I would now. But many of the episodes I was very proud of. I became a fan."

"Monk," which aired on USA from 2002-09, has plenty of fans, enough that Peacock decided to reunite most of the cast of the detective drama (Bitty Schram, who played Monk's nurse for two seasons, is the only notable absence). Peacock has made a cottage industry out of reviving NBCUniversal TV shows, airing three reunion films of USA's "Psych"). And after resurrecting Monk for a COVID lockdown-era PSA, the streamer wanted more.

"The response was so overwhelming," Shalhoub says. "We thought, people want to see this character come back." Peacock agreed, and thus began Breckman's binge-watching of his own TV show.

Shalhoub, 70, who won three Emmys for playing the high-maintenance but lovable Monk (and was nominated for each of its eight seasons), it was even easier to get back into character. "It took us maybe a day or two to find the voice again," he says. "But it came. ... It felt like 14 years was 14 days."

The film finds Monk at a low place. Not since the death of his wife (which predated the original series) has his mental health been so poor, and he has the COVID pandemic to blame (he's a germaphobe with high anxiety). At the movie's start, Monk's former assistant Natalie (Traylor Howard) and former police colleagues Randy Disher (Jason Gray-Stanford) and Leland Stottlemeyer (Ted Levine) reunite in San Francisco for the wedding of Monk's late wife's daughter Molly (Caitlin McGee).

Of course, since this is "Monk," a mysterious death the day before the wedding has them all working one last case.

Shalhoub says the cast's reunion mirrored that of the characters. "The airport scene when Monk first sees Natalie and Disher, that was scheduled first," he says. "We were really meeting up again."

But it's not all hugs, reunions and cartoonish villains. "Last Case" goes to a dark place with Monk's mental health, as the series did occasionally over its eight-year run.

"We're coming back after 14 years, and that forced us to raise the stakes. It's big. The crisis should be real and significant in order to justify coming back," Breckman says, adding he was inspired by Frank Capra's seminal Christmas movie "It's a Wonderful Life." "It beautifully weaved in dark moments. But I think everyone remembers that movie as life affirming and very positive."

Shalhoub agrees that "Monk" is ultimately uplifting. "We always have tried to honor the fact that OCD is serious and very disruptive to people's lives, to families and relationships," he says. "And we've always tried to destigmatize (it) and to billboard the notion that a person's liabilities can be turned into assets."

But what about that title. Is this really Mr. Monk's very "Last Case"?

As far as Shalhoub and Breckman are concerned, Mr. Monk could come back any day.

"If it was up to me, I would love to continue the journey," Breckman says. "I hope the fans respond and (we can) make another installment worthwhile."

"I never say never," adds Shalhoub. "Neurotic detectives with certain special skills: I guess there seems to be a an endless appetite for that."