Trenton Colman is a creative thirteen-year-old boy with a knack for all things mechanical. But his talents are viewed with suspicion in Cove, a steam-powered city built inside a mountain. In Cove, creativity is a crime and "invention" is a curse word. Kallista Babbage is a repair technician and daughter of the notorious Leo Babbage, who died in an explosion--an event the leaders of Cove point to as an example of the danger of creativity. Working together, Trenton and Kallista learn that Leo Babbage was developing a secret project before he perished. Following clues he left behind, they begin to assemble a strange machine that is unlike anything they've ever seen before. They soon discover that what they are building may threaten every truth their city is founded on--and quite possibly their very lives.