Wartime tale of a group of British scientists efforts to develop the first radar system. They did it just in time for it to be used in the Battle of Britain against the might of the Nazi Luftwaffe. Without it the little island could well have been overrun.

Returning home from a shopping trip to a nearby town, bored suburban housewife Laura Jesson is thrown by happenstance into an acquaintance with virtuous doctor Alec Harvey. Their casual friendship soon develops during their weekly visits into something more emotionally fulfilling than either expected, and they must wrestle with the potential havoc their deepening relationship would have on their lives and the lives of those they love.