Ambassadors Day takes place thousands of years in the future, when the remnants of the human species have moved indoors to escape the wrath of an environment turned hostile. Many generations have passed, and all that's left of communication between these isolated sanctuaries of humankind are the Ambassadors.

Long after the End of the World has passed into myth, two envoys meet to exchange the weekly numbers of their people. It is a day like any other in Rendezvous Zone Eight-Seven Northwest, until one of the Ambassadors is ordered to shoot the other. Refusing, the Ambassador tries to defuse the situation. Unfortunately the problem began thousands of years ago, and there is nothing anyone can do about it. Rocks are thrown in glass houses, kettles are called black, and everyone manages to get their feelings hurt. When the dust has settled, the world is changed forever.