Nine—and Death Makes Ten (1940)
Blurb:
My review:
A tautly written tale of murder onboard a munitions-carrying ship travelling through submarine-infested waters. Although the fiend has left his fingerprints at the scene of the crime, those fingerprints do not match anybody's onboard; a neat variation on the impossible crime. Which of the nine credible characters did it is solved by H.M., also alert for Nazi agents, but not alert enough to prevent his being coshed. The solution, based on Hans Gross and a bottle of ink, is quite brilliant.