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.