Ashore on leave, Captain Sir Thomas Kydd learns of a dismal harvest and general hardship among the population. In Germany, Napoleon Bonaparte is celebrating victories that once again make his name feared throughout Europe. An armistice is signed and while the Allies lick their wounds Bonaparte sets to preparing for a grand advance. And, in a fragile peace, and saddled with huge war debts, the government has no choice but to place HMS Thunderer, along with many other Royal Navy ships, in reserve, until the Navy can decide what to do with their great fleets.
Meanwhile, Kydd is offered an admiral's flag but this is the West Africa station and the anti-slavery operations set in fever-ridden swamps. Despite the obvious dangers and hardships, Kydd sees this as the realisation of his life's ambition and readies for sea in his beloved Thunderer as his flagship.

In a turn of the tide Bonaparte is defeated by the Allies and exiled to the tiny island of Elba. Then electrifying news breaks out - the tyrant has escaped and is marching on Paris, the citizens flocking to join him.

The British government as well is rocked by a realisation that Napoleon's invasion fleet is still in being and if the French navy declares for him they can sail from the ports now free of blockade and make the invasion of England a reality. The Channel Fleet has been stood down, its ships in various stages of repair, its commander on leave in the country. There's one man in active service who happens to be on the spot - Admiral Sir Thomas Kydd. With frantic haste he's appointed temporary commander-in-chief to sail with all the men-o'-war that can be scraped together to stand athwart the French. Kydd knows this will probably mean the sacrifice of not only his ships but himself and his men.

He calls on subterfuge and daring to flaunt defiance and resolution until the Battle of Waterloo settles the matter. Then, he has the satisfaction of seeing Napoleon Bonaparte carried off to St Helena, from whence he can never return.