Something Nasty in the Woodshed by Anthony Gilbert.
First published 1942; cover shown is the 1944 paperback by Canadian Collins White Circle Books.
The cover art's not that brilliant - I just love the title!
Anthony Gilbert (1899 - 1973) was the pseudonym for British novelist Lucy Beatrice Malleson. She published 69 crime novels, many covering the cases of lower-class lawyer Arthur Crook, who was known as "the criminal's hope, the judge's despair."
Malleson grew up in a poor family and supported herself from her late teens onwards - no mean feat in the early 1900s.