The Captain’s Vengeance picks up where Havoc’s Sword ended. Alan Lewrie and HMS Proteus are scouring the Caribbean to find a valuable prize that disappeared from Prince Rupert Bay, Dominica before a Prize Court could condemn it. The most likely suspect is a surly pressed seaman, Toby Jugg, who has a wife and children in Barbados. They visit his home and find his real name is Paddy Warder and he has an extensive history as a sailor and privateersman. However, she has not heard from him in some time.
Major spoilers follow.
Lewrie gives up his search and reports to the commander of the Jamaica Station whose flag captain, Sir Edward Charles, intensely dislikes Lewrie. Much to his surprise he finds that Sir Edward deceased and replaced by another captain who is something of a friend, Captain Nicely whom he met in Haiti (Sea of Grey). He also finds that his missing prize crew has been found marooned in the Dry Tortugas and are now recuperating in Kingston.
While questioning the recovered sailors, Lewrie becomes convinced that Jugg knows a lot more than he is telling.
Nicely decides that the pirates who took Lewrie’s prize are a threat to commerce that must be dealt with. Based on what they have learned from the marooned seamen, they believe the pirates are operating out of New Orleans. Working with the agent of a British trading company which is licensed by the Spanish to deal in Florida and Louisiana, they hit upon the scheme of taking Lewrie and a handful of his men into New Orleans to locate their prize and the pirates. Much to Lewrie’s chagrin, he finds that he will again be working under the guidance of former army captain James Peel (King’s Commander, Sea of Grey, Havoc’s Sword). Peel reveals that Toby Jugg sailed with one of the men who marooned him in the past as a privateersman.
Lewrie enters New Orleans in the guise of a cashiered Royal Navy officer who is now working with the trading firm of Panton, Leslie & Company to command their flotilla of small boats trading upriver from New Orleans. He quickly experiences the political ferment in New Orleans as long time French residents chafe under Spanish rule and American filibusters encroach on Spanish territory.
He encounters a group of Americans. While he quickly suspects they are American soldiers sent to reconnoiter New Orleans as a move preliminary to an American invasion, they also aren’t convinced that Lewrie is who he claims to be. The two sides establish a sort of armed truce in which they watch each other carefully.
Lewrie’s presence has also caught the attention of the pirate band. They are motivated by a desire to return Louisiana to French control and are attempting to fund a revolt against Spain out of the proceeds of their piracy. The leader of the band, Charitė de Guilleri, attempts to find out Lewrie’s motives and becomes smitten with him, and he with her.
In addition to finding the stolen prize, which is discovered by Toby Jugg, Lewrie works with Gideon Pollock, the agent of Panton, Leslie & Company, to develop a plan for how the British might seize New Orleans without a protracted overland campaign from Florida.
Charitė de Guilleri notices the leader of the American soldiers following her and sends her brothers out to kill him. He escapes but is recognized and an assassination attempt against him is organized.
The assassination attempt fails but the American is wounded. Lewrie stumbles onto the attempt and is nearly killed. The Americans blame Lewrie, who they are now sure is also scouting New Orleans for an invasion, for the attempt.
The attempt was made with a unique weapon only recently sold in New Orleans by Panton, Leslie. From the sales register they are able to determine the purchasers. Using the social network of slaves and free blacks known to Pollock’s New Orleans mistress, Lewrie and Pollock are able to determine Charitė de Guilleri’s true identity and they connect her to the man who bought the weapon.
In the meantime, the pirate band has learned that a large shipment of silver currency is scheduled to arrive in cash-starved Louisiana. They set out to intercept the shipment and their sudden departure is noted by Pollock’s network. Nothing is kept very secret in New Orleans and one of the officers from the Panton, Leslie ship has heard rumor of the treasure shipment on a bar. Lewrie and Pollock quickly put the two events together and Lewrie departs New Orleans for Proteus which is patrolling out in the Gulf of Mexico. On the way out Lewrie’s men burn the prize they has lost from Dominica and accidentally burn an American trading ship also.
With the seizure of the treasure ship, the piratical group begins to fall apart. The older men in the group know that Spanish authorities will quickly figure out who took the ship and they wish to retire with their earnings.
Based on Toby Jugg’s experience as a privateersman in the Gulf, they believe the destination of the pirates will be Barataria Bay.
Proteus catches the pirates ashore and dividing their plunder. A short, fierce engagement ensues in which Lewrie kills one of the older pirates. The younger ones are killed fighting Proteus’s sailors and marine, and Charitė de Guilleri manages to escape. A small boat led by Toby Jugg catches up to the last of the older pirates. He offers them a share of his loot if they will let him go. The sailors agree, take the loot and desert.
Charitė de Guilleri makes it back to New Orleans. Her parents send her to France to get her beyond the reach of Spanish authorities. Though a lot of the Spanish silver is lost when the treasure ship burns, enough is recovered to make Lewrie wealthy.