Down in the pine-forested Franklin Canyon of the Santa Monica mountains, weary, slaphappy NCIS cast members are laying odds on which of them will be killed off in tonight's terror-tormented season finale (8 pm/ET on CBS).With the five final pages of the script unavailable to the actors, no one knows for sure who it will be. They just know one of them won't make it to Season 3. "We're all so tired at this point, if someone is dying, you sometimes wish it were you," quips star Mark Harmon (Special Agent Gibbs), taking a breather during filming. Executive producer Donald P. Bellisario promises an end that will not disappoint. "It's not truly a cliff-hanger because it's final," he says. "But it's unique and we'll be thinking about it into the first couple of shows next season." In this episode, the execution-style murder of two Navy lieutenants escalates into a case of international terrorism. Evidence points to the medically astute operative named Ari (24's Rudolf Martin), who once famously held Ducky (David McCallum) and Kate (Sasha Alexander) captive in the morgue. In the cold darkness of the encounter, Ari grabbed Kate waaay too close, wounded Gibbs and escaped with the stealth of a master spy. Earlier this season, Gibbs plugged Ari with a bullet to the shoulder and left him to suffer. "Gibbs takes Ari very personally," Harmon says. "But that's the way it is with the real NCIS guys. They all have cold cases that never leave them." In the finale, the hatred boils over as Ari, who once professed to be working for the Mossad but is now working for Al Qaeda, unleashes the organization's deadly vengeance on Gibbs and his NCIS team, who have been weakened from an outbreak of bubonic plague the week before. (Michael Weatherly's Special Agent DiNozzo got the worst of it.) Kate is assigned to be Gibbs' protector and he has to take her orders. "Yep, Gibbs looks pretty horrified when he finds this out," says Alexander, tucking a wisp of her shoulder-length hair under that black NCIS cap. She'll have her hands full, though, what with DiNozzo sick — and about to take the brunt of an explosion. Things aren't looking so good for rookie agent Timothy McGee (Sean Murray), either. As the cast shoots retakes and swats mosquitoes in the heart of this wildlife preserve, the real money is on poor, eager-to-please McGee to die in service to NCIS. What are the odds? "Two to one," Murray says. All speculation ends tonight.