NCIS taunted fans last week with an episode in which Tony DiNozzo (Michael Weatherly) was nowhere to be seen, only three weeks before he leaves the building for good. So that got us thinking: How will Tony be written out of the show? Executive producer Gary Glasberg told TVGuide.com last month that the writers have been working on the May 17 season finale (a.k.a. Tony's final episode) for months now, so what have they come up with?

Here are six theories about why and how Tony will say goodbye:

1. He'll get killed off. Don't worry, Tony fans: Surely Glasberg and Co. wouldn't be cruel enough to kill off a fan favorite, so we can probably rule out Tony DiNozzo going out in a blaze of glory (and gunfire). Also, there's that whole teaser showing DiNozzo's colleagues saying goodbye to him - implying that his departure is his own decision. On to more plausible ideas ...

Here's the first footage of Tony's final scenes on NCIS

2. He's the mole. ::ducks to avoid objects hurled by devoted NCIS fans:: OK, we know. It's not the most likely scenario. But hear us out: Last week's episode revealed that there's a mole within NCIS who's leaking information about the British spy case, and is either directly or indirectly responsible for Fornell (Joe Spano) and MI6 chief Jessica Terdei (Sandra Nelson) getting shot in Gibbs' safe house. Tony was conspicuously absent for the entire episode, allegedly off in Russia chasing down a lead. Or was he? Glasberg says the British spy case "gets to a point where it connects to Tony and ultimately his departure." Tony betraying his colleagues would be quite the twist ending!

3. He runs off with a Russian bride. Let's say Tony really was in Russia last week. Maybe he'll meet a nice lady at the bath house there and make her Mrs. DiNozzo. He did make a similar offer to McGee, after all ...

4. He decides the job isn't worth the risks anymore. With Tom Morrow (Alan Dale) assassinated a couple of weeks ago, and Fornell's life hanging in the balance, maybe Tony decides to reprioritize his life and not put himself in harm's way every day. Could that have been what Glasberg was referring to when he said the British spy storyline connects to Tony leaving? A new career path as, say, a film critic would be much more appealing.

Finale Preview: Get scoop on NCIS and other shows

5. Ziva is gravely injured. Alright, now for the meatier theories. We know, per Glasberg, that "Tony's relationship with Ziva certainly will have an impact on his reason to depart NCIS." Further, Glasberg says that Tony's exit is prompted by "something that has a mammoth impact on him - and understandably, would take that significant an impact to have him step away from his NCIS family." We're pretty sure Ziva (Cote de Pablo) facing a life-or-death situation, as teased in the May 10 episode, would fall into this category. AND it could also tie in nicely with the British spy storyline, since the rogue agent has Ziva in his crosshairs.

6. Tony and Ziva live happily ever after. Of course, No. 5 and No. 6 are not mutually exclusive. How's this for a hypothetical: Tony rescues Ziva and realizes that he's been wasting the last few years stagnating without her. He decides to move abroad to be with the love of his life - after saving her life first, of course. We may have a winner!

How do you think Tony is going to leave NCIS?

NCIS airs Tuesdays at 8/7c.

(Full disclosure: TVGuide.com is owned by CBS.)