Mr. Pinkerton Has the Clue

Mr. Evan Pinkerton leaves the noise and smells of London to holiday in
the fresh air of Bath and enjoy the healing waters. To his dismay, a
murder is committed in the very hotel in which he is staying. The timid
Welshman is drawn into the official inquiry and is finally joined by his
friend and former lodger Inspector J. Humphrey Bull of the C.I.D.
Pinkerton has worked with Bull in the past as an unofficial detective
and has often been the person to finger the murder. This story takes
twists and turns that baffles the local police and yet Mr. Pinkerton
doesn't realize he has the clue until he sweats out a cold in one of the
famous baths. You'll be guessing until the very last chapter.
8. Mr. Pinkerton Has the Clue (1936)
David Frome is the pen name of Zenith Jones Brown, a.k.a. Leslie Ford. 1898-1983