Code Name: Diamond Head is a 1977 American spy film starring Roy Thinnes as an undercover counterintelligence officer known as Diamond Head whose mission is to stop a rogue double agent from stealing the formula for a new chemical weapon. Originally filmed as a pilot for a new television drama (which was never picked up by the networks), it eventually was as used for The NBC Monday Movie on U.S. broadcast network NBC. Johnny Paul (Thinnes) arrives in Oahu disguised as a flashy gambler and ladies' man. However, he is actually on a mission to stop the theft of a deadly new gas, which has the potential to cause instant death upon contact. The substance was being secretly created by a top battalion of Marines at the request of a Pentagon official. However, a double agent had infiltrated the unit, killed the executive, and assumed his identity. Paul uses his image to get close to the double agent, who is known by the pseudonym "Tree". However, once his cover is blown, it's a race against time to stop Tree from selling the secrets to an unnamed foreign power.