The Brass Cupcake — John D. MacDonald

In Flower City, a sleepy resort town on Florida's Gulf Coast, wealthy Elizabeth Stegman is murdered in a jewel heist gone bad - her missing jewels insured for £750,000.

It falls to hardboiled ex-cop Cliff Bartells to find the killer, retrieve the jewels and console the decedent's niece and only heir, beautiful and headstrong Melody Chance. But complicating Bartell's best efforts is a local police force that proves to be less than cooperative.