NCIS Season 4 Episode 13

Marine corps NBC preparedness liaison officer major John McGuire is found dead, locked up after a dose of BZ nerve gas. A camera traces the gas to terrorist Mamoun Sharif. Also on the case is the CIA, and to Gibbs's delight Army lieutenant colonel Hollis Mann while he gets charge. Ten kilos gas stolen from a lab which tests its effects legally, but with clever twists from both his accomplice and Sharif.