Redoubtable is the eighth book in the Kris Longknife Series. Kris Longknife commands Patrol Squadron 10, made up of corvettes. The vessels are disguised to resemble merchant vessels. USS Wasp is challenged by a pirate. Wasp engages the pirate and wins the battle. Kris attempts to take the pirates to Kaskatos. She learns that the planet, which was originally settled by people seeking isolation, has recently suffered an influx of refugees from the Greenfield Confederacy. Among the newcomers is a woman, Jackie Jackson, who was formerly a member of Greenfield State Security. She intends to take over the planet and present it to Henry Smythe-Peterwald XII. Her technique is simple: Hold hostages and kill them if their families don't cooperate.

Kris and her Marines under the command of Jack Montoya and Hernando Cortez engage Jackson and her thugs. They are successful and Jackson is killed. In the aftermath, Kris realizes that she has to build an infrastructure on Kaskatos. She leaves Penelope Lien and Hernando Cortez behind to work on that problem while she travels to confer with Victoria Peterwald.

After some exchanges about political and economic philosophies, both Vickie and Georg Krätz admit that Greenfield's government and economy are on the verge of collapse. Vickie tells Kris that she misses the counsel of former associate who disappeared after traveling to St. Petersburg and asks Kris to search for her, in part because Kris and her staff have dark enough skins to mix with the local population. Kris finds Vickie's missing friend and, while doing so, meets a local mayor and arranges for his city to be granted a charter signed by Vickie. Meanwhile, Cara leaves Wasp without permission and is abducted by pirates.

Kris deploys Patrol Squadron 10 in pursuit of the pirates; Admiral Krätz sends Greenfield forces to assist. The combined forces destroy the pirate nest on Port Royal.