Spooks - Series 6 - Episode 6

Despite the efforts of MI5 and the CIA, the team discover that Iran has acquired nuclear triggers. Adam feels guilty for having been duped by his lover Ana, and Ros knows her alliance with the shadowy anti-American cabal Yalta have enabled Iran. In a bid to target the courier and prevent him leaving the country, Adam and Ros get on a plane to Tehran. But they can't arouse suspicions of their mission, or else the terrorists will poison London's water supply.