A missile of extraterrestrial origin is hit by a Soviet missile, now it is out of control and making it's way across Canada, scorching everything in it's path. New York is due to be hit in about half an hour, which gives the US plenty of time to evacuate the city. They wouldn't be that efficient these days, it's take them a few hours to choose the font for the evacuation notices.
Top nuclear scientist Dr Loring (Robert Loggia) and his assistant/lover Ellen (Joan Wood) are due to get married when the alert goes up. Instead they work on Loring's plan to fire an experimental nuclear missile at the incoming menace. This involves carrying deadly plutonium across the city to the launch site with only the most minimal of security...
So, this film doesn't make sense on many levels but it is a genuinely exciting, tense and fast moving film. It is somewhat marred by incorrect stock footage. This isn't exactly uncommon with films (of any era to be honest) but it does feel like the makers threw every scrap they could at this film to pad it out. Despite the flaws this is a great watch.