Late in the nineteenth century, a Victorian scientist shows his disbelieving dinner guests a device he claims is a time machine. Respectable London scarcely has the imagination to cope with such an idea. But a week later, they reconvene to find their friend ragged, exhausted, and garrulous. The tale he tells is of the year 802,701, of life as it is lived in exactly the same spot, in what once had been London. He has visited the future of the human race and encountered beings that are elfin, beautiful, vegetarian, and leading a life of splendid idleness. But this is not the only lifeform that exists in Eden, for in the tunnels beneath paradise lurks man's darker side.