Jonathan Blake (Tyrone Power) is a waiter at Lloyd's Coffee House in the early days of the shipping insurance firm Lloyd's of London. Determined to climb high, he joins a Lloyd's syndicate and becomes rich and successful. A romance with the wife (Madeleine Carroll) of a brusque aristocrat ensues, ending in a climactic duel at the height of the Napoleonic Wars. Finding his childhood friend, Lord Nelson, in charge of the naval fleet, Blake acts to help win the Battle of Trafalgar.