Found: Crime fiction novel regarding some druglord I guess

There is this novel where the villian makes deals with big profile people while a Stradivarius violin is playing. They have to kiss his greasy hand to seal the deal. If broken, he makes there worst nightmare come true. There was some defence minister involved, some activist was going to be killed, his boyfriend was killed on the boat she was in with her sister. The detective is able to kill the villian when his only son betrays him. Also, I remember the author here maybe was a married couple.

Found: The nightmare by Lars Kepler

Touchstone: The Nightmare