Den of Iniquity by J.A. Jance

Retired Seattle cop J.P. Beaumont now has his private investigator's license. When he's asked by a friend to look into the death of Darius Jackson, who authorities had determined died of an accidental drug overdose, he agrees to help. Soon, Beau discovers other deaths similar to Darius' and wonders if they are all connected. In Beau's personal life, his grandson Kyle, has come to stay with Beau and his wife, Mel. Kyle, in his senior year of high school, doesn't want to live with his father, Jeremy and his new girlfriend, Caroline. As a favor to Kyle, Beau agrees to look into Caroline's background. In Den of Iniquity, Jance writes another solid entry in this long-running series.