Crimson Joy a Spenser novel by Robert B. Parker

Crimson Joy a Spenser novel by Robert B. Parker 211 pages.
A serial killer is on the loose. Three black middle-aged women are found naked, bound, gagged, and shot. A single red rose is found at the crime scene. A fourth black woman is found by her estranged husband. The fourth murder is almost, but not quite the same, as the other three.
Racial tensions are high and the city fathers need this to be solved. the husband of the fourth victim confesses to all four crimes. The city fathers are relieved, but Lieutenant Quirk and Detective Belson don't agree and are placed on "vacation".
Since they have nothing else going on, Quirk and Belson enlist Hawk and Spencer to work on the case. They determine that the killer is probably a cop. Spencer's beloved Susan has several cops under psychiatric therapy and would be a great resource. Unfortunately a red rose is found in the waiting room of  Susan's office.
"Who is it?" they ask. Susan's professional ethics and her own sense of dignity will not let her speculate, without concrete proof, even if she herself is in the crosshairs.
Now, for Spenser, it becomes very personal.
I thought I would read a few pages before bedtime, and finished the book at 1:05 AM. on a "school night". I really should know better...