This is the twentieth book in the series chronicling the adventures of lucky Jack Aubrey and his best friend Stephen Maturin, part ship's doctor, part secret agent. The novel's stirring action follows on from that of The Hundred Days. Napoleon's hundred days of freedom and his renewed threat to Europe have ended at Waterloo and Aubrey has finally, as the title suggests, become a blue level admiral. He and Maturin have at last set sail on their much postponed mission to Chile.