A non-human race, the Hurrians, has established a base on the Moon, waiting for humanity to blow itself up with its nuclear weapons. All known large-primate species, after all, have blown themselves up almost as soon as they invented nuclear weapons. After the inevitable conflict, the Hurrians plan to swoop down and help the survivors—for a price, of course.
When, after fifteen years, the war has failed to materialize, they feel the need to bring it about themselves but cannot quite bring themselves to do it.
This is certainly a memorable story, and the Hurrians make an interesting race, as does their dilemma (not to mention the vivid way in which the image giving rise to the story’s title is used).
The main mark against it is its blatant anti-nuclear war cautionary nature. As were many Americans in the 1950’s, Asimov was of course acutely ware of the danger and terrified of the potential results of a nuclear war, and he wrote a number of stories centered around the theme. This, as it happens, is one of the better ones, but the palate grows dull after so many of them, especially when they tend to be so heavy-handed, and so it gets marked down a notch.