The past has always haunted Special Agent Gibbs on "NCIS," but he will start to confront some of those demons in his recovery from last season's shooting.

The 13th season premiere will start in the immediate aftermath of the shooting as Gibbs (Mark Harmon) is rushed to a Navy hospital ship for emergency surgery. Following the surgery, the NCIS agent will drift in and out of consciousness and begin to have hallucinations of his late friend and mentor Mike Franks (Muse Watson) as well as other familiar faces, according to TVGuide.com.

"You have to remember that Gibbs is in a difficult place," showrunner Gary Glasberg told TVGuide.com. "He's going to see some things and talk with some people that might surprise everybody. It's no surprise that Mike is there, but there are some other people from his past who he also interacts with, in some really touching scenes."

The first promo also showed Gibbs reconnecting with his deceased daughter Kelly, but the gruff investigator also reconnects with those still living. In the second episode back, the NCIS team helps their boss' friend from the DEA on a case that keeps going cold. Gibbs' connection with his old friend "sheds a bunch of light on Gibbs' past and things that we still don't know about," Glasberg said.

One person fans shouldn't expect to show up in Gibbs' conscious or unconscious state is fan favorite Ziva David, played by Cote de Pablo, who exited the CBS drama at the beginning of season 11. "There'll definitely be some surprise appearances of people from our 'NCIS' past, but Ziva David is not one of them," Glasberg said.

While Gibbs' deals with his past, the team is trying to figure out their boss' new look after he ditches his standard military haircut and polo shirt for a modern cut and tailored dress shirt. DiNozzo (Michael Weatherly) also becomes curious of Gibbs' DEA friend in episode two and his mentor's determination to help the drug enforcement agent succeed.

"NCIS" returns for its 13th season on Tuesday, Sept. 22 at 8 p.m. on CBS.