A Killing Kindness — Reginald Hill

When Mary Dinwoodie is found choked in a ditch following a night out with her boyfriend, a mysterious caller phones the local paper with a quotation from Hamlet. The career of the Yorkshire Choker is underway. If Superintendent Dalziel is unimpressed by the literary phone calls, he is downright angry when Sergeant Wield calls in a clairvoyant. Linguists, psychiatrists, mediums -- it's all a load of nonsense as far as he is concerned, designed to make a fool of him. And meanwhile the Choker strikes again -- and again...