NCIS

We've talked at great length about the mystery of Rule #51, the endgame of M. Allison Hart, the motives of the Reynosa cartel and Gibbs' big decision on tonight's NCIS season finale.

In the episode, titled "Rule Fifty-One" (see photos and promo), it appears as if Gibbs has gone lone wolf in Mexico, with Director Vance trying to foster his own investigation in D.C.

How will it all play out for Gibbs - with the drug bosses and his own boss? We welcome your theories. For now, ET has compiled about two minutes' worth of clips from tonight.

Here's a glimpse of what Gibbs and Vance are up to ...