blow is a figure of speech

With the help of government-issued pamphlets, an elderly British couple build a shelter and prepare for an impending nuclear attack, unaware that times and the nature of war have changed from their romantic memories of World War II.

While recording sound effects for a slasher flick, Jack Terry stumbles upon a real-life horror: a car careening off a bridge and into a river. Jack jumps into the water and fishes out Sally from the car, but the other passenger is already dead — a governor intending to run for president. As Jack does some investigating of his tapes, and starts a perilous romance with Sally, he enters a tangled web of conspiracy that might leave him dead.