The war with the Peeps means the Manticoran Navy is stretched thinly, and can't provide cover for merchant shipping in Silesian space. Pirates are taking advantage of this, and Klaus Hauptman in particular is feeling the pinch. He concocts a plan, enlisting the help of Reginald Houseman, to get Honor Harrington to command a squadron of Q-ships --- merchantmen refitted with massive armament, but no armour, and a green crew --- because they realise she will probably be killed in the mission.
Honor agrees to the commission. She takes the squadron to Silesian space, and starts hunting pirates. Unbeknownst to anyone, not only is there a pirate fleet (rather than just individual marauders), but also a covert Peep operation to prey on Manticore shipping. However, the Peeps discover the pirates, too, and are outraged by their atrocities, so target them aswell. In fact, one Peep ship, at great risk to itself, actually 'rescues' Honor's ship Wayfarer from pirate attack (thinking it is an unarmed Manticoran merchant ship, not realising she is luring the pirates into a trap), and is subsequently captured by Honor. From the information from the captured Peeps, Honor locates and destroys the pirate stronghold.
Because the squadron was put together at short notice, her crews have a high proportion of raw recruits, and a high proportion of undesirables. The latter include Steilman, an altogether bad piece, a vicious bully who is planning to desert. [That Steilman was allowed to re-enlist a few years earlier is explained by the Manticore Navy knowing about the upcoming war with the Peeps, and so lowering their entry standards to increase their numbers. But I'm not convinced it would be possible for them to have lowered their standards enough to let Steilman through.] He picks on a newbie, Aubrey Wanderman, and beats him up badly. Aubrey is too scared -- both of what might happen to him, and to his friends -- to finger Steilman, but PO Harkness and the Marines take him under their wing and teach him single combat. [No mention is made of the fact that Honor didn't report Pavel Young's attack on her in the Academy, for fear she wouldn't be believed -- and look what grief that decision lead to -- but the resonances are there.] Later, when Steilman and his gang nearly kill his friend Ginger Lewis in an 'accident', Wanderman goads Steilman into a fight, and beats him to a pulp.
Wayfarer 's engineering officer, Harry Tschu, has been adopted by a female tree-cat, Samantha. Nimitz is interested! And by the end of the book, Samantha is pregnant.
For some implausible reason, Klaus Hauptman and his daughter decide to visit Silesian space, to get a first-hand picture of the problem. [I think this is a weak plot device: Hauptman may be arrogant, but is he really foolish enough to risk both himself and his daughter like this?] Naturally, they are attacked, by Peeps. Naturally, Honor rescues them, everyone thinking she is going to die in the process. Naturally, in the final, bloody, battle of the book, she doesn't. However, Hauptman realises he has been wrong about Honor, and apologies to her.