This is Perry's third world, or fourth if you count Earth. In the first, there was Richter, a brilliant scientist who gave Perry a working suit of power armor before dying to an attack by an adversary that seemed to come from nowhere. In the second world, he became a knight fighting in a war against a callous enemy. There are others like him, thresholders, always in opposition, and it's becoming clear to Perry that this is going to be his way of life, hopping from world to world. Now he finds himself in a place that's doing its best impression of Victorian London with the serial numbers filed off, with a new enemy that will test all the knowledge and power he's accumulated so far.