Mankind discovers a method of energy transfer with the aliens of another universe that promises unlimited energy. Unfortunately, it also promises ultimate destruction. Only a few scientists are capable of seeing beyond their own self-interest and hubris to recognize this fact, but can they make others believe? Asimov has constructed an admirable allegory for the environment quandry that we face here on earth, although he fails to show how limitless power would transform our lives.
The novel is constructed in three parts. The first and third sections involve human beings and rely too much on telling and not enough on showing--lots of long, didactic conversations and far too little incident. The third section is particularly weak; it is dull and bloodless with a take on human sexuality which is supposed to be advanced but, from today's standpoint, seems firmly mired in a seventies mentality.
The triumph of this novel is the masterful middle section. Asimov depicts an alien society that is truly unlike mankind, yet he manages to depict distinct individuals. This is quite surprising coming from a writer who is known neither for characterization or alien-building. It's just a shame that the rest of the novel could not maintain this quality and had to end on such a tragically dull note.