In Season 2, Episode 22 ("SWAK"), an envelope emblazoned with a red lipstick kiss and addressed simply to "NCIS Special Agent" arrives in the bullpen at NCIS headquarters. Insisting that he "recognize[s] the lips and the scent," DiNozzo frees the letter from the grasp of NCIS Special Agent Timothy McGee (Sean Murray) and excitedly cuts it open. However, DiNozzo immediately regrets his swift action when a mysterious white powder erupts from the envelope.
Because of fears the substance could be an anthrax attack, DiNozzo and Cait are quickly whisked off to Bethesda Naval Hospital. While anthrax is quickly ruled out, McGee suggests alternatives could include everything from talcum powder to cholera. Eventually, it is discovered that the substance is a form of pneumonic plague. While Cait tests negative for the substance, DiNozzo is not so lucky and quickly becomes ill. In an effort to comfort DiNozzo, Cait also claims to be infected and stays with DiNozzo as long as possible. Eventually Cait is forced to leave the containment area as DiNozzo's condition worsens. As Cait departs the facility, NCIS Chief Medical Examiner Donald "Ducky" Mallard (David McCallum) attempts to comforts her, but she simply cries, "He's dying, Ducky."
Even worse, Gibbs' efforts to retrieve an antidote are ultimately unsuccessful. DiNozzo is only given a 15% chance of surviving, but Gibbs suddenly becomes very sure that his protege is going to survive. "You will not die," Gibbs insists, motivating DiNozzo with a slight head slap. While he struggles to get the words out, DiNozzo eventually responds, "I got you, boss." Of course, DiNozzo eventually makes a full recovery and continues to appear on the next 11 seasons of the series, before exiting at the end of the Season 13.
