If Swift's job title sounds familiar, that's because it is. The Office of Special Projects is also the focus of NCIS: Los Angeles, and is described as one of NCIS' most elite units that specializes in undercover work. It's worth noting that "Past Due" is not a crossover episode, though, so Swift won't be bringing Callen, Hanna or Hetty along with him.

However, he can be a huge help to Tennant (played by Vanessa Lachey) in the season's last two episodes.

It's a role that is completely in Henry Ian Cusick's wheelhouse. He's played agents and other men of action before, most recently in the third and final season of the ABC thriller Big Sky. Cusick had a recurring role as Avery McCallister, who married Beau Arlen's (Jensen Ackles) ex-wife Carla.

Before that, the actor had developed a history of playing various mysterious and/or highly skilled characters, which made him a perfect fit to help NCIS: Hawai'i further explore Tennant's CIA history.