"The Malinsky Massacre" A Third Murder Mystery planned by J.G. Links and written by Dennis Wheatley. 1938 Hutchinson and Co. Publisher, 32-36 Paternoster Row, London, UK

In Great Britain in the 1930's "crime dossier" mysteries were apparently popular. The reader received an entire packet of stuff associated with an unsolved crime. This one is over 100 pages. It starts off with a letter from a British policeman to a mystery writer (the reader) asking him to please try to help solve this double murder that happened in 1899 and remained unsolved. The author (reader) says he would be delighted and the policeman sends him all of the evidence. Old letters, maps, photos, newspaper clippings and even a crushed up poison pill found at the crime scene. After sifting through 90+ pages of evidence the reader tries to solve the crime. Inside the back cover is a sealed 10 page document solving the crime for the reader. This one is completely intact, never opened...the mystery remains unsolved.

The synopsis is stated briefly on First Editions 1938-1939

The Earl of Malinsay is dead, and ruin comes to an ancient family.  Did the valet really murder his master, or did the mysterious foreigner send poisoned sweets to Viscount Raeburn?  Whose handwriting is on the label and who put arsenic in the peppermints?  Is the beautiful Countess conspiring with her lover or is the secret of the Malinsays hidden in the past?

You have all the clues.
Can you discover the truth before you open the sealed section containing
THE SOLUTION?

A more extensive discussion of British Crime Dossiers in general and Dennis Wheatleys work in particular can be found on the Digital Antiquarian

5th Earl dead in bed.

6th Earl as found dead.

 Various hooligans, no-accounts, rounders and rakes...all suspects.

More great evidence can be found below and the book is available for purchase here.