Consider the poor mailman of the future. To "sleet and snow and dead of night"--things that must not keep him from his appointed rounds--will be added, sub-zero void, meteors, and planets that won't stay put. Maybe he'll decide that for six cents an ounce it just ain't worth it.
Witness Mr. Henry Bemis, a charter member in the fraternity of dreamers. A bookish little man whose passion is the printed page, but who is conspired against by a bank president and a wife and a world full of tongue-cluckers and the unrelenting hands of a clock. But in just a moment, Mr. Bemis will enter a world without bank presidents or wives or clocks or anything else. He'll have a world all to himself... without anyone.
After some sudden and unspecified catastrophe has depopulated England, the countryside reverts to nature, and the few survivors to a quasi-medieval way of life. The first part, The Relapse into Barbarism, is the account by some later historian of the fall of civilisation and its consequences, with a loving description of nature reclaiming England. The second part, Wild England, is an adventure set many years later in the wild landscape and society.
The conversion of light into electricity by spectrum is an interesting possibility. The idea of using foreign proteins on the human system to repel enemies, is also interesting. Do you get it? We didn't either until we read the story. Read the yarn and you'll get it too.