The time traveller

he traveller plodded slowly across the long, cobbled bridge. Rain spat from the sky, pounding against the cold road, mist and cloud blocking any sunlight that could brighten the occasion.

He could feel the clock digging into his back as he walked. It went everywhere with him, or rather he went everywhere with it. The clock was the key to everything; the key to moving through time and space. It was what had allowed him to see everything that had been, and everything that had not yet come to pass.

Life as a time-traveller had its benefits, but it also took its toll...
  if he changed something from the past, it could probably make him not exist. If he wanted to get  the world tidy, he needed to take a risk about his and other people's existence and use the key for the clock. The clock was the key to everything; the key to moving through time and space. suddenly, the clock started picking all rubbish in the world and melted it into a liquid. 
he forgot that the clock had special powers that it uses it for good.