Lady Hamilton's love affair with Admiral Nelson rocks the British Empire.

In 1782, Emma Hart, the beautiful daughter of a cook hired by artist George Romney, is courted by his friend, Charles Greville, but later marries Greville's uncle William, Lord Hamilton, the British ambassador to the Court of Naples. Despite the differences in their ages and social positions, Emma and Lord Hamilton are happy, and Emma becomes a confidante of the Queen of Naples. Years later, Emma meets English Capt. Horatio Nelson and, during the Napoleonic wars, is instrumental in gaining royal permission for him to take on badly needed water and provisions at Naples. Although initially denying their feelings, Nelson and Emma soon become lovers and live openly together. Nelson's naval victories against the French, and Emma's help to the British government during the war, lead to their return to London where they are cheered by crowds. However, because of their adulterous relationship, Emma is snubbed by English society and shunned by her husband. After Emma is denied an invitation to a royal ball in Nelson's honor, Nelson leaves his wife Fanny and retires to his country estate with Emma. They are happy for a while, but duty later calls Nelson away to head the British fleet. Although he again defeats the French, Nelson is badly wounded and dies at the Battle of Trafalgar, surrounded by his loyal men and thinking of Emma.