The British receive intelligence that an anti-nuclear militant group is planning to kill the U.S. ambassador at the Iranian embassy. The British Special Air Services enlists the help of Capt. Peter Skellen (Lewis Collins), who is charged with going undercover. But he is quickly found out by the terrorists, and his wife and child are taken hostage. As Skellen attempts to get word to his superiors, the terrorists begin to execute their plan, which leads to a siege at the embassy.