"A Dame Walks Into Your Office ..."
From the back cover:
"A dead body, no witnesses, and a room full of suspects with perfect alibis. Can you find the killer and bring him to justice? Learn the secrets of mystery fiction – and what will, and will not, work in RPG mysteries. Learn how to be a better investigator. Learn the problems you are likely to encounter in a low-tech, magic, super-tech, or horror mystery."
Originally released in PDF form, and later as a small print-to-order book. Has four completely blank pages in the back