Don't Cry For Long (Mac #11), by Thomas B. Dewey (epub/Kindle/pdf)
A slightly shady congressmen... His sulky 18-year-old daughter... A dead bodyguard... And blackmail!
It's all in a day's work for Mac, the Chicago detective. Another classic entry in the detective series that could have been ripped from today's headlines -- but written in 1964. #11 in the classic series.