On the edge of a century's turning, London was a sprawling mosaic of crooked tile roofs, shuttered windows, cobblestone streets, and garbage-strewn alleyways. Fog crept through the city like pestilence, mixing with the foul breaths of smoke from coal grates and great belches from factory smokestacks. Cold buildings huddled together as if seeking warmth against the nights chill.

Nearly two millenia of history had seen London evolve from a Roman settlement to a Saxon stronghold, then a burgeoning commercial center and religious axis. Ultimately, London became a pinnacle of European political might as well as a powerful industrial hub. World-shaking events would begin — or end — here.

For decades now this place had endured the turns of the industrial revolution, which had transformed it from a grand city of one million inhabitants into a vast metropolis teeming with more than four times as many people, all of them trying their best to survive.

In the distance Big Ben chimed its lonely but predictable tones. Most people no longer even awakened to the clock towers hourly ritual, especially not so late. The steady sequence of gongs drifted past like a lullaby, reassuring the city's sleeping inhabitants that all was well.

Big Ben fell silent again, and so did the streets.

Then a low rumble started deep underground, as if the convoluted sewers near the Thames suffered from indigestion.

In Moorgate Passage, a pair of dogs hungrily dug through garbage in search of edible scraps, as they did every night. They half-heartedly snarled at each other, too hungry to notice the mysterious sounds.

But the noise rose steadily in volume, like buried, restless thunder. The ominous trembling grew louder and louder, shaking forcefully until it rattled loose roof slates and chimney pots…