Covered in dog hair, Obsessed with books, Wondering what it's all about. I suspect the answer is ice cream and the ocean.
Third book in a series of English mysteries set just after the first world war. Many mysteries have a troubled cop, detective, etc... at their heart but in this case the Scotland Yard detective is literally haunted... or mad. Ian Rutledge is a talented detective but he came back from the war with a heavy conscience and the spirit of a scottish soldier that he had shot for disobeying orders squatting in the back of his mind. Whether this is a real supernatural twinge or Rutledge is suffering from severe PTSD is kept purposefully vague.