Reiko is an unusual character - a Samurai class woman whose father allowed her to train in marital arts, and a clever detective who helped Sano when he was the Shogun's chief investigator. Now, with few outlets for her mental energy, she has begun helping those who write to her. She's done some good, freeing abused wives from marriages and bringing the killer of a pregnant peasant teen to justice, but she's also made enemies. Did one of those enemies frame her for murder?
Reiko has been found - by Hirata, Sano's former right-hand-man and now successor as chief investigator - in the bed of a murdered and mutilated daimo. Reiko can't explain how she got there, her memories don't make sense, and the daimo's widow claims Reiko was her late husband's lover and killed him in a jealous rage. Rowland interweaves Reiko's mystery with the political machinations of competing factions in the Tokagawa Shogunate which may lead to Sano's execution for treason. Like one of House's patients, everyone Sano, Reiko, and Hirata meets lies, or tells a tale too remarkable to believe.
Red Chrysanthemum is a tightly plotted mystery, with all threads (including the false leads and red herrings) getting neatly tied up in the end. Because I read paperbacks and almost always know that there will be a next book, I was never really concerned that Sano or Reiko would be executed, but I was mostly pleased at how Rowland 'saved' them. I have one minor quibble, though, and it's with Hirata. He seems to bend to the needs to the plot and occasionally against his known character, and his actions in the climactic scene have a hint of deus ex machina. Still, this is a good entry in what has been a remarkably even-quality series.