Hidden Depths (Vera Stanhope #3) by Ann Cleeves. 2007/2018. Softcover.

A hot summer on the Northumberland coast, and Julie Armstrong arrives home from a night out to find her son murdered. Luke has been strangled, laid out in a bath of water and covered with wild flowers. This stylized murder scene has Inspector Vera Stanhope and her team intrigued. But then a second body - that of beautiful young teacher Lily Marsh - is discovered laid out in a rock pool, the water strewn with flowers. Now Vera must work quickly to find this dramatist, this killer who is making art out of death. Clues are slow to emerge from those who had known Luke and Lily, but Vera soon finds herself drawn towards the curious group of friends who discovered Lily`s body. What unites these four men and one woman? Are they really the close-knit, trustworthy unit they claim to be? As local residents are forced to share their private lives and those of their loved ones, sinister secrets are slowly unearthed. And all the while the killer remains in their midst, waiting for an opportunity to prepare another beautiful, watery grave...