"The man who commits adultery with another man's wife, he who commits adultery with his neighbor's wife, the adulterer and the adulteress, shall surely be put to death." -- Leviticus 20:10
Four youngish wives of older wealthy men have been intimate with the same man, someone who can upset their marriages in very fundamental ways. Spenser is called in to help. His sense of the situation shifts as he gets to know the players. Are there any innocents here? Probably not.
For most of this story, you will learn about the lusts and pleasures of irresponsible people. Now, some such stories attract readers because they are titillating. This one isn't. Other such stories draw an audience because there's a lot of humor involved. This one lacks that element. What it does have is a portray of some really shallow people enjoying themselves without much concern for anyone else. I thought that was a real downer.
Much like many of the more recent Spenser books, The Professional turns into a morality tale in the end. But it takes a long time to get there. It wasn't much worth the wait to me. I thought this was one of the weakest books in the series. These books require some interesting conflicts, difficult situations, chilling villains, and action. You will look in vain for those elements here.