Let X be the murderer

'Let X be the Murderer' was published in 1947. It is a bleak November morning when Sergeant Martin, Inspector Charlton s stalwart sidekick, receives an agitated phone call from Sir Victor Wallingham claiming that a ghost attempted to strangle him in the night. When Inspector Charlton follows this up, he is blocked at every turn, but even so, when the following night does actually end with the discovery of a body, he is not expecting it.