Sharif Returns (S04E13)

After 10 kilograms of highly toxic chemical weapons go missing, Gibbs and his team scramble to locate it. The NCIS team is horrified when they discover that the deadly chemical weapon is now held by wanted terrorist Mamoun Sharif. As Sharif taunts them with phone calls, Gibbs and the team unite with Army Lt. Col. Hollis Mann (Susanna Thompson) to find him before he carries out his plan to attack major U.S. cities with chemical warfare. (CBS TV Network)