Today is FBI Agent Fornell's lucky day.  After leaving his bulletproof vest on by chance and after an attempt on his his life, he's forced to team up with NCIS and his pal, Agent Gibbs, to solve the case.  And, guess who's at the center of it all and the actual case -- their lovely ex-wife Diane Sterling.  Diane's investigation with the IRS lands her in harm's way, nearly gets her ex killed, and poor McGee is assigned to protect her.  McGee is the gentleman, but that still doesn't stop his ruthless co-workers from spreading rumors about his alleged escapade with the former Mrs. Fornell, Mrs. Gibbs, or Mrs. whatever she is these days.