One year has passed since the events of The Honor of the Queen. The Havenite government has finally run out of alternatives to ward off its long-dreaded economic collapse. Reform is impossible, at least not without triggering massive unrest amongst its vast subsidized population and terrorism from homegrown extremist groups. The People's Republic must expand or die, but the many single-system nations it has targeted are banding together into an alliance led by the Star Kingdom of Manticore. War between Haven and Manticore is now inevitable, but if the People's Republic plays its cards well, it might just be the short, victorious war it needs to calm down the Proles, bring vast new sources of income to its depleted coffers, and even provide a convenient excuse to institute reforms. The People's Navy is tasked with planning a campaign of aggression that will, in time, lead to open warfare.
Back at the Star Kingdom of Manticore, Honor Harrington has spent a year on medical leave at her homeworld of Sphinx, to recover from the physical and psychological wounds suffered on Grayson, until she receives orders from the Manticoran Admiralty: she has finally been cleared to return to active duty and been given a new ship to command. To Honor's elation, she has been selected as captain of the brand-new battlecruiser HMS Nike, which is not only the latest bearer of the Royal Manticoran Navy's proudest legacy, but also a ship uniquely suited to Honor's skills as a starship commander.
Another pleasant surprise for Honor comes when she finds that Commander Michelle "Mike" Henke, her best friend and roommate at the Naval Academy (not to mention first cousin to Queen Elizabeth III of Manticore and seventh in the line of succession to the throne) has also been assigned to Nike as her executive officer, along with some other officers that have served under her on her last two commands.
Honor also gets operational orders: upon completing her shakedown tests, Nike is to report to Hancock Station, a brand-new fleet base near Havenite-controlled space, to serve as Rear Admiral Mark Sarnow's flagship. However, with the growing tensions between Manticore and Haven, substantial elements of the Royal Manticoran Navy are deployed to Hancock Station, and Admiral Sarnow goes from being the local commanding officer to just a battlecruiser squadron commander under Vice Admiral Sir Yancey Parks, and the most junior of Parks' subordinate commanders at that. Sarnow may be glad at being given Nike and Honor for his squadron, but Parks is less than happy; he honestly considers that no matter how brilliant and skilled Honor may be as a starship captain, her temper and aggressiveness may be the last thing a frontline command such as his needs when that region of the galaxy is at the edge of full-scale war.
Nike's deployment to Hancock Station has a less than promising start: construction defects on one of her fusion plants cause significant damage during the voyage from Manticore, and the brand-new battlecruiser must spend the next months docked at the station for major repairs. To compound the bitterness of seeing her new command turned into a lame duck for the time being, Honor finds that she is being shut out of the task force briefings, even though by rights she should be invited as Admiral Sarnow's flag captain.
The only silver lining during these first months is the relationship that Honor starts to build with Captain Paul Tankersley, the head of Hancock Station's repair teams, and a cousin of Mike Henke to boot. Their companionship turns to friendship, and eventually into love, and Honor ends up having to deal with romantic issues she had always shied away from, both due to self-esteem and personal image issues, as well as from the attempted rape she suffered at the Naval Academy.
Meanwhile, Haven steps up a campaign of aggression across the frontline systems of the Manticoran Alliance. What began as provocative deployments of force escalate to the destruction of sensor equipment, raids against Manticoran merchant shipping, and finally to ambushes against isolated Manticoran vessels. Haven's trump card in this campaign is the "Argus Net", a series of stealth sensor platforms deployed at the edge of allied systems and which can be surreptitiously queried by Havenite warships to get updates on all fleet activities.
As tensions escalate, Manticore and her allies step up their preparations for war. Local Manticoran commanders at the frontline are given oficial war warnings and are instructed to do their best to avoid war, but not to the detriment of their commands' safety or the security of the systems they are defending. In response, Admiral Parks decides to deploy most of his forces to three nearby Alliance member systems, leaving Hancock under the protection of a small detachment commanded by Admiral Sarnow until further reinforcements from Manticore arrive.
Unbeknownst to the leaders of the People's Republic, trouble is brewing both abroad and at home. After analyzing the pattern of the Havenite incursions, the Manticoran Admiralty believes it can lure part of Haven's fleet to Yeltsin's Star by planting false orders to withdraw several warships from the system, when it is actually reinforcing its presence there. The bait works and the head of the Havenite Navy himself, Fleet Admiral Amos Parnell, personally leads a large task force to attack Yeltsin's Star.
Meanwhile, the Havenite commander facing Hancock Station, Admiral Yuri Rollins, finds out through the Argus Net that most of Admiral Parks' forces have left the system; in the knowledge that Manticore's most important base in the entire region is now bereft of capital vessels and ripe for the taking, he decides to send his fleet to seize control of Hancock. Both prongs of the planned Havenite initial offensive have independently decided to jump the gun on their carefully-laid out plans.
On Haven itself Robert Stanton Pierre, the speaker of (what passes for) the Havenite Parliament, has decided to take his long-standing rage and frustration at the continuous mismanagement and militaristic adventurism of the People's Republic ruling clique of "Legislaturalists" (of which he's excluded on account of his lower-class background) to the level of staging an actual conspiracy to topple the government, with the assistance of domestic terrorist groups and disaffected members of the Havenite military and security services.
Nike has finally concluded her repairs and joins her squadron mates in a series of exercises and tactical maneuvers, and Honor assists Admiral Sarnow in preparing Hancock Station for the eventuality of a Havenite attack, all too aware that though they have done an ingenious and totally unexpected use of what little resources Admiral Parks has left them with, they won't be capable of resisting a full-scale invasion of the system until either Parks returns or Manticore sends additional reinforcements. Some reinforcements, though, arrive at Hancock Station, but Honor is dismayed to find out that these include the heavy cruiser HMS Warlock, still under the command of her old nemesis, Captain Pavel Young, who is still out for her.
During an exercise, some destroyers of Admiral Parks' task force fortuituously discover one of the Argus sensor platforms, and the Manticoran admiral realizes in horror that the Havenites not only know the location of his forces, but also that Hancock Station has been left dangerously deprived of warships. He gives orders to his dispersed forces to regroup at Hancock as soon as possible, but it will take time that the station does not have.
A large Havenite fleet commanded by Admiral Rollins arrives at the Hancock System in force, though the Havenite commander opts to keep most of his forces in reserve and ready to jump away in case that the Manticorans have laid a trap. The defending fleet under Admiral Sarnow can track the invading fleet through its FTL sensors and pulls out several tricks during the engagement: clever approaches under ballistic power to achieve the best optimal position to launch a massive missile barrage without being detected, bolstering their firepower with towed pods capable of firing large amounts of additional missiles, electronic warfare drones that mimic the emission signatures of a squadron of superdreadnoughts, and even a minefield to which they lure the Havenites.
These tricks cause heavy damage to the Havenite fleet although they are not enough to turn the tide of battle, as the invading forces simply have too many ships, including dreadnoughts that far outgun whatever Admiral Sarnow has under his command. As a last ditch effort, the Manticorans offer themselves as bait with a radical course change. Since the Havenites have a second force that can take the base, the initial force turns to pursue, hammering the fleeing Manticoran fleet and destroying many ships.
HMS Nike herself is hit, and Admiral Sarnow is gravely injured and left unconscious. Honor assumes command of the task force instead of passing it to Sarnow's ranking officer on another ship, as she knows that Manticoran reinforcements have entered the system and they have to hold out just a little longer to ensure that the Havenite force can't escape. Unfortunately, a panicked Pavel Young orders a squadron of cruisers under his accidental command to scatter from the fleet, compromising the defense of the task force and refusing to return even when Honor orders him directly to resume formation.
The sacrifice of the Manticoran task force pays off, and the Havenites are trapped by the incoming reinforcements. Though most of Admiral Rollins' forces return to their base, Admiral Parks' reassembled fleet attacks the Havenite base and lay waste to their forces in the sector. Combined with another utter debacle at Yeltsin's Star, where Admiral Parnell lost almost half his fleet to the Manticoran ambush, the war begins with a brutal mauling of the best elements of the Havenite Navy.
On Haven, Pierre's conspiracy seizes on the disastrous news coming from the frontlines to mount an attack against the Presidential palace using naval assault shuttles to give the impression of an attempted military coup. The Havenite President, almost all of his Cabinet and most of the ruling elite of the People's Republic are killed, and Pierre announces that he is "reluctantly" taking over the government as head of a new "Committee of Public Safety" to deal both with the war abroad, and with the threats at home.
HMS Nike is ordered back to Manticore, both for repairs and to bring the thoroughly disgraced Pavel Young to a court martial, and Honor receives Admiral Parks' thanks and his apologies for the way he treated her in the past.