Rinehart, Mary Roberts -- Miss Pinkerton aka The Double Alibi (1932)

Poor Miss Adams -- aka 'Miss Pinkerton' for her detectival achievements! She is perpetually promised -- or is it threatened with? -- matrimony by Inspector Patton, but all she ever gets are murder cases. She is called in by Patton on the very first page to look after the elderly invalid Juliet Mitchell, whose no-account nephew Herbert Wynne has apparently shot himself in his room. But why are the police taking such a close interest? There are footsteps in the attic, noises on the stair, two more deaths and a good deal of had-I-but-knowning before the mystery is eventually cleared up and the killer identified as the person you guessed it would be, a long time ago. Still, there are a few clever twists and a little humour, and Rinehart's accomplished story-telling makes the long journey worthwhile.

Jon.