In the late nineteenth century, when Conor Broekhart discovers a conspiracy to overthrow the king, he is branded a traitor, imprisoned, and forced to mine for diamonds under brutal conditions while he plans a daring escape from Little Saltee prison by way of a flying machine that he must design, build, and, hardest of all, trust to carry him to safety.

In the summer of 1851, with encouragement and ideas provided by his family, an inventor builds a working submarine and takes his family for a ride. Includes notes about Lodner Phillips, the real inventor on whom the story is based.