 When the USA satellites photograph many flying saucers coming to Earth, the American President James Dale has a meeting with his advisors. He is convinced by Professor Donald Kessler (Pierce Brosnan) that Martians would be a developed culture and therefore peaceful by nature, in spite of the warnings of General Decker (Rod Steiger). The authorities, some civilians and the press prepare a welcome committee for the aliens, but they realize that Mars is actually attacking Earth.