The rifle platoon of USMC Second Lieutenant George Armstrong Craster, transported by helicopter during ordinary exercises taking place in South Korea, did not at all expect to fall into the past - to August 1950, to the famous Busan Perimeter. Despite the fact that Craster and his men ended up they were simply stunned by the phenomenon that had fallen on their heads; this did not in any way affect their discipline, sense of duty and confidence in the high combat capabilities of the Marines of the 21st century. Having clarified the situation, the lieutenant discovers that his platoon is the only force capable of standing in the way of a North Korean detachment trying to stab in the back a South Korean regiment fighting hard in a nearby mountain valley. The collapse of the defense of the South Koreans, who are barely holding back the onslaught of the enemy, threatens to create a gap in the perimeter and, who knows, perhaps even change the course of history. The prospects of the communists capturing and evacuating a helicopter that made an emergency landing make Craster even more terrified. In order to prevent this capture and preserve the technologies of the future for American scientists, Lieutenant Craster's Marines are only required to hold the eye of the needle of a mountain pass until the platoon Help is welcome...