Dee is on vacation after some tough work, and is on a fishing trip in quiet "Rivertown" where he hopes to relax. However, he is contacted by the local authorities, including an Imperial princess who makes her residence at a riverside palace there. The Princess is horrified at the loss of a valuable pearl necklace, a gift from her father, and her camp in the palace is worried that this is part of some scheme to manipulate the Emperor. Also, there's the death of a hotel clerk, and the disappearance of the owner's wife, that complicates things.
This is the next-to-last Dee novel written, and by now van Gulik had abandoned the named three cases and the map of the scene in the beginning. However, it's got some good characters, including the plucky niece of the innkeeper, Fern, whose assistance to Dee is invaluable. There's also a roving Taoist monk, Master Gourd, who proves to be more than he seems. There's also a nice glimpse of palace life, indolent and luxurious on the surface but full of scheming and decadence underneath.
Well, of course they are. But it's fun on the way. We get a good look at Magistrate Lo, a character often depicted as foolish and frivolous, but this time we're allowed to see a shrewd, intelligent side to his character. There's also some side characters, like the poet Sexton Loo, whose beliefs are a precursor of Zen, and the tragic Saffron, a mentally ill girl who lives in a nearby Shrine of the Black Fox.
One interesting aspect is Yoo-lan, who is based on the real Chinese poetess Yu Xuanji, who really was a courtesan who became a respected poet, reportedly had an affair with great poet Wen Tingyun, but whose life ended on the scaffold after being accused of the murder of a servant, a charge that is debated to this day. (According to some sources, that story may be completely false.) One of Yu's poems is reproduced in the book, in a scene set in a pavilion during an autumn banquet, a scene I found very memorable.
There's a few weaknesses in this entry; the plot's a little thin and hurriedly resolved. But van Gulik was writing this while very ill, and it was published a year after his death, so perhaps his talents weren't at their full peak.
For a bit of irony, the next book in the sequence of the series is the first written....