Battle against the French continues to wage in British waters, and Acting Lt. Horatio Hornblower has been commissioned to capture and detain the French vessel Le Reve. His mission is accomplished with great success, earning them reward and notoriety among the fleet. In honor of this achievement, he's asked to accompany Captain Pellew to a high-society function where he meets the Duchess of Wharfedale (Cherie Lunghi), an unusual woman with somewhat vulgar habits and forward interest in politics. Her husband has recently died, leaving her a vast inheritance and a desire to return home to England. Hornblower has been asked by Pellew to sail the frigate back to Britain, and take on the duchess as a passenger. Not overly pleased with this circumstance, Horatio is somewhat elevated in spirit by a particular commission.

Confidential papers containing prudent naval information are to accompany him back to England. If they're boarded or if there's even a threat of being taken captive, his orders are to dump them overboard. The first few weeks of their voyage pass without excitement but then they come into the throes of a storm. In order to avoid being dashed upon the rocks, Hornblower alters course, taking them further out into the center of the channel. Here they find themselves in the middle of the Spanish Armada. Making a vague attempt at passing themselves off as a French-occupied ship, they're asked to surrender or be fired upon. In a momentary decision, Hornblower allows the duchess to take the documents and conceal them on her person, believing they won't be so indecent as to commit her to a search. Horatio and his crew are taken to a Spanish prison, where one of his crew, the ambitious Hunter (Christopher Fulford), makes premature plans for escape.

To his surprise and horror, already imprisoned on the island is Archie Kennedy (Jamie Bamber) who was lost to them months ago when his dory slipped moorings. He was believed dead, but is instead found senseless and given to epileptic fits. Horatio must determine a method of bringing his friend back to full help, making his escape from the island accompanied by all of his men, and keeping Hunter and his mutinous lot under control. In addition, he's having grave doubts about the tractability of the duchess. Intrigue abounds as the young naval officer contends with insurmountable odds, and eventually proves the worth of his word. Few men would stand by their honor as Horatio does, which alone makes this episode outstanding. It holds only moderate action but the presence of the duchess as a dangerously charming and yet at times vulgar woman balances out the time spent in a prison cell.

There is initial violence when they attack and take command of the French vessel, but their later surrender is without bloodshed. There are some fistfights and struggles, and a few men are shot and killed and/or wounded. Archie is prone to violent epileptic fits. Horatio is locked in a sewer sell for several days as punishment for not revealing the deeds of one of his men. A man drowns in a storm. There's also the usual profanity, some of it from the duchess' lips. Hornblower sweeps off his hat and cheerfully says under his breath "GD him to hell!" while saluting a French officer. There's a sexual element at work with the presence of the duchess, but it's never overt. She jestingly trades innuendo with dinner guests, and flirts with a French commander. It's intimated they spend the night together as bribery to keep his mouth shut about her true identity. (Nothing is seen aside from later references and her inviting him into her room.) Hunter speculates that the only thing on Horatio's mind is how he can "board the duchess," but our hero is sweetly embarrassed by her vulgarity. When she pulls up her skirts and stuffs papers into her garters, he turns away rapidly. His innocence is refreshing and sweet, as is the final conclusion. One of the finest things about this film is the underlining respect between Captain Pellew and his officers. They all appreciate and admire one another for their naval talents, but even more... for their honor. 

When the captain gives the men a chance to recant a promise made on their behalf by Hornblower, none of them want out of it. They admire their leader that much. Lindsay does a remarkable job with Pellew, giving him just the right blend of stuffy upper-class attitude blended with good-natured enthusiasm and sheer brilliance in battle. This may not be one of the more bloody and adventurous of the Hornblower installments, but it's certainly one of the most intriguing.