An unusual blend of science fiction and contemporary history. The history of the U.S. from 1945 to 1975 was essentially as represented in this story. However, in this story, what happened was not determined by the principal actors themselves, but was manipulated by an alien being who had advanced scientific knowledge and the power to operate on minds which made it possible for him to insinuate himself into the process. On the other hand, his problem was the fact that this particular alien came from a world which was nearly a carbon copy of the Earth and was essentially indistinguishabe from earth dwellers, including at the emotional level. Consequently he ended up having a wife and son on his home planet and a wife and daughter on this one and was emotionally attached to all of them. When the time came for him to throw the switch to blow up the earth, he was caught on the horns of an insoluble dilemma.