Mark Harmon’s ‘NCIS’ Comeback Has His Colleagues Nervous: ‘He Expects 110 Percent From Everyone’

Mark Harmon‘s much-anticipated return to the NCIS Universe has his colleagues sweating, a source tells Closer.

On Tuesday, June 30, CBS announced on Instagram that the 74-year-old actor will be reprising his role as Special Agent Leroy Jethro Gibbs in season three of the prequel series, NCIS: Origins.

“Mark officially retired and said he wouldn’t be coming back, so the fact that he’s doing this says a lot about where his head is at,” says the source. “This isn’t about having fun or taking another victory lap. He’s coming back because he feels a real responsibility to get the franchise back on track.”

While Harmon’s comeback will bring a “huge boost” to the show, the source notes, “there’s also a lot of nerves because nobody expects him to take it easy.”

The two-time Emmy nominee “may come across as this quiet, laid-back guy but behind the scenes, he’s incredibly driven,” says the source,” and [he] expects the same level of commitment from everyone around him.”

Harmon is also an executive producer on Origins, “so he’s got a huge amount of authority,” reveals the source. “There’s a ton of pressure to impress him and with Mark, there’s no room for coasting” during filming.

“He expects 110 percent from everyone on the cast and crew and if anyone isn’t pulling their weight, they’ll hear about it,” the source says. “He pushes himself just as hard as he pushes everyone else, so it’s not a case of him being unfair. It’s just that his standards are sky high.”