From the Game's Introduction:
The Age of Gears lasted long into the nineteenth century. And then the darkness came. One day, the skies darkened into night and the morning did not dawn. Darkness covered the world. Within days most higher life forms were dead or dying. Mankind had a small supply of food but in a world without refrigeration, soon mankind was dying. After a few months, the only living creatures on Earth were the clockmen. Confusion nearly did them in, there was no one left to serve. Up until then most clockmen were stationary, grandfatherly figures who taught young people in living rooms, or student from the front of university classroom. The construction factories researched better and better self-ambulating designs.
Just as suddenly as it started, the darkness ended 122 years later. During that time, the clockmen transformed themselves into the image of their former makers. Mobile clockmen wore clothes and bustled about the cities in harsh whisper of whirring gears and clanking latches. To differentiate themselves from their forefathers, the mobile clockmen started referring to themselves as watchmen. This is their story.