Classic 12-Chapter Mystery Formula– This article outlines the standard formula used by mystery writers through countless stories in the past century for Whodunnit’s and Cozy Mysteries.
The Two-Body Plot: A Useful Four-Act Murder Mystery Structure – Writer John P. Murphy outlines the story structure used by author P.D. James and others. A really good article, and worth reading for anyone planning to write a murder mystery.
Frank Gruber’s “Fool-proof” 11 Point Formula for Mystery Short Stories – Pulp mystery writer Frank Gruber used this “formula” to sell over 300 short stories starting in the 1930’s. It’s less a formula than a checklist, but definitely a good one!
How To Write A Murderously Good Mystery – Writer Karen Woodward has a take on the Hero’s Journey structure that applies it to Murder Mysteries that might work for some writers. You could probably turn this into a 11-12 chapter book pretty easily using her structure.
A Plot Begins to Take Shape – Author Margot Kinberg outlines the typical plot patterns used in Classic, Cozy, Noir and Police Procedural mysteries.
The Guilty Vicarage: Notes on the detective story, by an addict – Written in 1948, this article from Harpers magazine goes into incredible detail about the nature and structure of classic murder mysteries.
The Detective Conan Mystery Formula – This is an outline of the typical two-part plot formula that the very long running Manga/Anime series Detective Conan (aka Case Closed in English) uses for most of their mysteries.
The Technique of the Mystery Story – This book on writing mysteries was written by Carolyn Wells in 1913, and is now public domain and available on Project Gutenberg. Despite the age, Wells does a good job of exploring mysteries as they were in her time, and it’s an interesting look at the classic murder mystery formula.