The case in question was investigated in the 16th episode of "NCIS" Season 4, entitled "Dead Man Walking" — not to be confused with the 1995 movie of the same name that nabbed Susan Sarandon the Academy Award for Best Actress. This "NCIS" episode featured a Navy lieutenant named Roy Sanders (Matthew Marsden) who shows up in the MCRT bullpen and isn't looking too good. He comes to the team with a simple request: to solve a murder. His own murder, in fact. No, he's not a ghost visiting them from beyond the grave; as he demonstrates by removing a clump of hair, Roy has realized he's been poisoned with radiation and will meet an untimely end. It turns out he works at the International Atomic Energy Agency, but doesn't believe his sickness is mere occupational hazard.
The team manages to suss out how Roy's been poisoned — Abby (Pauley Perrette) isolated radioactive ash from a shooting range and Ducky posits that the thallium has been laced into Roy's cigars — but has yet to figure out to figure out a motive. That is, until Gibbs puts together that Roy is due to go to Uzbekistan to inspect a nuclear reactor. Given that he'd made a similar trip six times previously, it's likely that he would have noticed the changes that have been made recently, changes that appear to be geared toward re-establishing a Soviet-era weapons program at the site. All it takes is a $50,000 bribe to IAEA admin Holly Stegman (Erin Torpey) for her to poison Roy. Sadly, her goal was simply to prevent him from making the inspection trip and she's dismayed to learn he's dying.
