A guest blog kindly contributed by Dennis Sherwood, who runs the Silver Bullet Machine consultancy.
Twelve pairs of eyes looked intently at the small, dapper, moustachioed figure at the head of the table.
“Your case is very like another I solved only recently,” he said. “Whilst a train was snowbound, a savage murder was committed. There were two possible explanations. Either the murderer had boarded the stationary train, violently stabbed the victim, and then escaped. Or…”
He paused, and made eye contact with each of the twelve people around the table. “Or… the twelve passengers on the…