The Wikipedia synopsis:
The story concerns the sighting of a UFO which appears to have crashed in the San Fernando Valley, after which massive interference with teleradio transmission brings FCC investigators into action. They, in turn, begin encountering reports from people of seeing what appears to be a man dressed in a bizarre outfit. Their investigation uncovers that this is a being from outer space who, to escape capture, removes his spacesuit and proves to be invisible. The invisible being running loose sets off a massive manhunt and public panic.