Scene: babbage machine versus child

A massive mechanical computer, building-sized, beneath the earth. Rusted iron catwalks and ladders run crazily through massive grinding brass and stone gears and clouds of dust. Rotating pillars throughout the structure glow from within with red-hot energy....

traps...

a small child, clutching a leather sack, calling for help as she rides a gear (the catwalk above which gave way). How to get to her before the slowly rising gear crushes her against another? The nearest catwalk is 10 feet away, and looks none too sturdy itself.

Complicated by: once involved in rescuing the girl, an attack by the guardians of the machine: tiny dexterous gremlins that grasp and claw, dressed in leather vests with dozens of pockets, wielding vicious curved wrenches.

The sack contains a tiny device: a glowing gemstone surrounded by several oddly shaped moving silver gears. What is its purpose? The girl does not know.