Forgotten Book - Who Killed Robert Prentice?

The first Crime Dossier created by Dennis Wheatley and J.G. Links was Murder off Miami (in the US, File on Bolitho Blane) and it proved to be a huge success, bringing together Golden Age elements such as the 'challenge to the reader' in a dossier format, like a three-dimensional version of books such as The Documents in the Case by Dorothy L. Sayers and Robert Eustace. 

A follow-up was inevitable, and it came in the form of Who Killed Robert Prentice? which boasts some intriguing clues as part of the package. Unfortunately, since the clues include a particular perfume on certain correspondence, they don't always stand the test of time. When copies turn up on the second hand market, items are often missing - my first edition lacks an important newspaper cutting as well as some face powder (!) but one curiosity is still present and correct. This is a little wallet of pieces of a torn-up photograph - which turn out to display a topless woman in the company of a man: in other words, it's a compromising picture used for the purposes of blackmail. Racy for 1937, that's for sure.

The British police are baffled by the death - by strychnine poisoning - of the wealthy Prentice. His widow contacts a visiting American detective called Schwab and asks him to look into the case. He soon finds that there are several plausible suspects, including the deceased's step-son and his mistress. 

After some intricate stuff concerning alibis, it eventually becomes clear that the crime turns on a plot device which is by no means original (I associate it with another strychnine poisoning mystery, which in other respects is very different) but which still works pretty well in this context. This was actually the first Crime Dossier I ever read, and rereading it thirty years later was equally pleasurable.