Why "the wife of the Fifth?" ?

I am a fan of Douglas Kennedy, I read 7 in less than a week, Because rain continues on the Brittany Bay as DK (finally his hero in Swindle: excellent) compares -in addition to the cold- SF. For both ... I express doubt, but good. LOL LOL ... This "Woman in the Fifth" I was not at all excited, there is a well-crafted plot is DK, but the string is too big, the environment is very underground, underworld, not rejoicing, the universe of the homeless or "sleep dealers" is an odd Paris, a Paris that I do not know anything, yet Paris is my city .. The plot might well have happened elsewhere DK gives the impression of not liking Paris. And this "Woman in the Fifth" that arises as a fairy or a witch, may be an ectoplasm, a kind of ghost. To read if there is nothing better to read or do!