Cue the jazzy guitar intro and rev up the helicopter.

“Magnum P.I.,” the reboot of the popular Hawaii-based detective show, started filming again today, reborn after a summer of uncertainty prompted by CBS’ unexpected announcement in May to cancel the show, despite solid ratings.

Frustrated fans launched a campaign to save the show, and NBC responded, ordering 20 new episodes. Ten of the new shows, comprising Season 5, are expected to begin airing in January, with the remainder airing the following season. NBC reportedly has left the door open for more episodes.

A traditional Hawaiian blessing was held for the cast and crew Monday at Barber’s Point, where filming for the new season opened. Afterward, cast members spoke of their surprise at the announced cancellation, the relief that it had found a new broadcast home and the gratitude they had for fans who helped save the show.

For Stephen Hill, who plays former Marine and helicopter pilot Theodore Calvin, aka T.C., the cancellation came at a particularly inconvenient time. After years of being “frugal” while building his career, he had splurged on a penthouse apartment in Waikiki. “We were hearing, ‘You guys not only are going to get picked up, but you’re going to get two seasons,” he said.

Fellow cast member Zach Knighton called him with the bad news. “I was like, ‘Am I moving in, or am I moving out?” he said. “I could not believe that we were not going to go forward. I felt like we had so many unanswered questions for the characters.”

Hill took some consolation in having another project lined up — the role of Buster in the film version of “The Color Purple: The Musical.” He was working on that film when he heard that “Magnum” was saved, which gave him a shot of adrenalin on set.

“You just get to hold your head a bit higher. There’s a bit of pride associated with having this job,” he said, crediting his work on the show for helping him land the film role.

He also had a touching experience this summer attending memorial services for Roger E. Mosley, the original T.C., who died Aug. 7 from injuries sustained in a car accident. Mosley’s friends told him that Mosley had praised his portrayal of the character. Hill even wore a T.C.-style hat to the services, giving it to one of Mosley’s relatives.

Mosley had appeared on the reboot as a storytelling barber, and Hill had hoped that it would lead to other storylines. “I will cherish that for the rest of my career, the rest of my life,” said Hill, who added that he otherwise hopes his character can expand on a budding relationship with a woman named Mahina, played by Emily Alabi.

He was especially grateful that not only he, but the entire cast and crew, had their jobs saved, saying they had become very close. “It’s more than job stuff now,” he said. “Over the course of four years, it’s like family.”

He’s given a name to fans for saving the show, giving them a name: “MP Eyes.” “Because they watch us,” he explained. “They’re like the investigators from the other side of the cameras.”

Knighton, who portrays former Marine and bar owner Orville “Rick” Wright on the show, looks at the roller coaster ride that “Magnum P.I.” has been on for the last few months from the perspective of an experienced screen actor.

“I’ve been a part of shows that have been canceled and then they have these fan campaigns trying to save it, and they never got saved, so I was skeptical,” he said, “but I just think the numbers were so good, it didn’t make sense to anybody.”

An Oahu homeowner, he spent much of the downtime working on his new home, but he kept track of the campaign to save the show. “They got a billboard in Times Square, they sent something like thousands of lei to NBC,” he said. “They did pretty amazing things for this little show, so the takeaway I got is, ‘Wow, people like this show a lot more than I thought.’ ”

Knighton’s character is facing a new challenge this season. At the end of Season 4, Rick became a father in a somewhat true-to-life scenario. Knighton’s wife in real life, Betsy Phillips, portrayed the mother — in the show, the couple are not married and are struggling with their relationship — and the couple have three children, two toddlers and a 12-year-old.

“I think the writers are going to have to start giving me some writing credits, because they’re going to be written from the headlines,” he said with a laugh.

He expects the show to delve into the romance between Magnum, portrayed by Jay Hernandez, and Higgins, played by Perdita Weeks. After years of simmering tensions, the two characters kissed at the end of the Season 4 finale. “I have a funny feeling we’re going to be dealing with that kiss,” Knighton said. “It will be interesting to see where that goes.”

“The saving of the show by NBC was such a blessing,” he said. “My boys were born here, and we plan to stay. We just want to be part of this community, and needless to say, we’re just really excited.”