Heretic, traitor, or prophet — Timothy Johnston must learn what he is as worlds move towards the start of an invasion of the earth that will leave it in mediaeval darkness. A fugitive from the invaders, the gifted Dhitha and the blood-drinking Veligit, Timothy is carrying plans that, if he delivers them to the earth's authorities in time, may forestall the invasion, but will betray his friends to capture — possibly even to torture and to death. The voice within him — the voice that some call prophecy — seems to be telling him, however, that nothing is how it seems to him. He knows only that, when he chooses, he will send two worlds down a path that will end in fire.