Lonely Magdalen is a 1940 mystery detective novel by the British writer Henry Wade.^[1] It was the fifth in a series of seven novels featuring the character of Inspector Poole, published during the Golden Age of Detective Fiction.^[2] The book focuses more closely on police procedural than the traditional puzzle format.^[3] There was a thirteen-year gap between this and the next entry in the series Too Soon to Die.

https://en.wikipedia.org/wiki/Lonely_Magdalen

A woman is found strangled on a corner of London's Hampstead Heath, who proves to be a prostitute from Kentish Town. The investigations of Inspector Poole, however, reveal that she had once been from a respectable background. He deduces the culprit is like to be drawn from one her clients.