When his father is killed fighting for the Union in the War Between the States, thirteen-year-old Tom Carroll must take a job to help support his family.He manages to find work at a bustling ironworks in his hometown of Brooklyn, New York, where dozens of men are frantically pounding together the strangest shipTom has ever seen. A ship made of iron .

Tom becomes assistant to the ship’s inventor, a gruff, boastful man named CaptainJohn Ericsson.He soon learns that the Union army hasvery importantplans for this ironship called the Monitor . It is supposed to fight the Confederate “sea monster”--another ironclad--the Merrimac . But Ericsson is practically the only person who believes the Monitor will float.Everyone else calls it “Ericsson’s Folly” or “the iron coffin.”

Meanwhile,Tom’s position as Ericsson’s assistant has made him a target of Confederate spies, who offer him money for information about the ship. Tom finds himself caught between two certain dangers: an encounter with murderous spies and a battle at sea in an iron coffin …