Admiral Hornblower in the West Indies is the final novel in C. S. Forester's "Horatio Hornblower series," featuring Captain Hornblower. While the other novels were set during the Napoleonic wars between France and England, this final novel is set during peace time, and Hornblower has received a promotion to rear-admiral and been sent with his fleet to the Caribbean to be stationed in the West Indies as commander. The novel details Hornblower's many adventures and near escapes as he serves as commander over the Caribbean.
Once he arrives in New Orleans, the most populous port of Louisiana, now owned by the United States since the Louisiana purchase from the French in 1803, he learns from those still loyal to Napoleon that there is a plan afoot to free Napoleon from isolation on St. Helena. Ex-French general Cambronne had commissioned a US ship and planned to load it up with French troops and munition and head to St. Helena to free Napoleon. Once Hornblower learns Cambronne's plan, being devoted to doing anything to maintain peace, Hornblower decides the best course of action to thwart Cambronne is to lie and say Napoleon is dead. While Hornblower's lie succeeds in thwarting Cambronne, Hornblower feels that lying was beneath his dignity as an admiral and decides to resign only to learn that Napoleon has indeed died.
Another one of Hornblower's duties while in the West Indies is to obstruct the slave trade, which the British abolished through the Slave Trade Act of 1807. Later, Hornblower fails to overtake a Spanish slave ship, it being too fast for his British fleet. To solve the problem, Hornblower follows the slave ship to a neutral port and succeeds in sabotaging the ship to the extent that its rudder is separated, enabling him to easily capture the ship. However, months later, Hornblower is taken prisoner by Spanish pirates who demand being pardoned for their slave-trading crimes. But Hornblower is able to escape and fire on the pirate ship.
More months later, Hornblower meets Ramsbottom, a rich wool merchant claiming to be on a tour of the Caribbean aboard his yacht. However, the truth is that Ramsbottom is on a mission to help the Spanish South American colonies gain independence. While Hornblower is away with his fleet, Ramsbottom sabotages a Dutch ship, taking the Spanish weaponry from its cargo. Upon his return, Hornsblower sees what has happened to the Dutch ship and also learns that the colonists have been successful in defeating the Spanish in a recent battle. Hornblower takes Ramsbottom's yacht just before Spanish and Dutch frigates arrive. He even manages to prevent war between the Dutch and the Spanish by persuading the Dutch captain to sue Ramsbottom, which he knows is a ridiculous suggestion that will never come to pass.
For his final adventure, his wife Barbara has come to join him in his last days as commander over the Caribbean and to accompany him on the journey back home to England where he will retire. Their journey home proves to be difficult as they encounter an off-season hurricane. While his seamanship saves the ship from completely sinking, the ship is damaged, but he and Barbara are rescued a few days later by a ship passing and safely return to England.