Through the Wall — Patricia Wentworth

MISS SILVER INVESTIGATES
Lying lifeless at the bottom of a jagged cliff, Helen Adrian made a ghastly sight. The clues clearly suggested she had not simply misstepped -- Helen Adrian had been pushed! But who would want to murder such an enchanting young creature? The prime suspects were a ne'er-do-well actor and a temperamental musician, but even so the evidence was exceedingly scant. With a murderer still on the loose, the authorities were lucky, indeed, that Maud Silver was there to help solve this most baffling mystery.

MAUD SILVER, PRIVATE ENQUIRY AGENT
She is everyone's favorite spinster detective. In her black cloth coat and with her ever-present capacious knitting bag, she appears every bit the proper Victorian governess, which indeed she once was. Now she has taken on the much more lucrative occupation of private enquiry agent. Armed with the tenacious common sense of the British and an uncanny ability to see into the very souls of murder suspects, Miss Silver is as memorable as the finest creations of Agatha Christie.