It was a bolt from the blue.

Donnie Wahlberg has revealed what convinced him to join the upcoming “Blue Bloods” spinoff, “Boston Blue,” after the original series ended last year following an impressive 14 seasons.

Wahlberg, 56, opened up about the decision during a special screening and Q&A for the premiere episode of “Boston Blue” in New York City on Tuesday, Oct. 14, per People.

He explained that the idea for the spinoff first came together after two different ideas “bumped into” each other. One involved his character, Danny Reagan, moving to Texas, and the other involved a new law enforcement family based in Boston.

“I think they were like, ‘Hey, instead of moving to Texas, why don’t we talk about him joining this thing and moving to Boston?’” Wahlberg, who was joined onstage by co-star Sonequa Martin-Green, said.

“But I really didn’t think that would ever happen anytime soon,” he added. “I was just chugging along in ‘Blue Bloods.’”

“Suddenly it was like, ‘Do I really wanna do a spinoff?’ I didn’t know. And this idea was really good. And the script was really good,” he shared. “I looked at it and I saw the possibilities of weaving the ‘Blue Bloods’ world into it, and I saw a chance to play Danny in a different way.”

However, Wahlberg admitted that he wasn’t fully on board for “Boston Blue” until he realized that his onscreen son, Sean (Mika Amonsen), would also be a police officer and therefore the spinoff’s entire dynamic would be different from the original.

“That suddenly changed everything,” he explained. “Now there’s a whole new world.”

“It’s not only Danny with a new partner, meeting this new family,” Wahlberg continued. “It’s Danny being a dad and worrying about his son, making sure he gets home safe every day and teaching him the job, the way that his family taught him the job.”

“Blue Bloods” premiered on CBS in 2010 and ran for 14 seasons before coming to an end in December 2024.

Following the Reagans, a family deeply involved in New York City law enforcement and public service, the original series starred Wahlberg, Tom Selleck (Frank Reagan), Will Estes (Jamie Reagan) and Bridget Moynahan (Erin Reagan-Boyle).

“Boston Blue,” meanwhile, was announced in February 2025 and will follow Wahlberg’s character after he takes a position with the Boston Police Dept and is partnered with Lena Silver (Martin-Green). It premieres Friday, Oct. 17.

Although Wahlberg opened up about the highly anticipated new series earlier this year, he made sure not to give too much away and ruin it for the original’s millions of fans.

“It was definitely a challenge to take on this opportunity, but I kept saying to myself, you know, if I’m really sincere about wanting ‘Blue Bloods’ to carry on, here’s an opportunity to do it,” he told Fox News Digital back in May.

“Now, it’s just Danny going to this new world, but I can’t say a lot about it — but I could say, if he’s a Reagan, it will never be just Danny,” Wahlberg added. “There’ll always be a Reagan a phone call away. And the traditions that the Reagans have, Danny wouldn’t abandon those traditions.”