Dr Black lies murdered in the cellar. That much is certain. But who killed the doctor? Was it Mrs White, the housekeeper, Miss Scarlett, the femme fatale, Professor Plum, the Oxford academic, Colonel Mustard, the colonial officer, Mrs Peacock, landed lady or the affable Reverend Green. What was the weapn? Revolver, lead pipe, spanner, rope, candlestick or dagger. The body shows signs it has been moved: was the scene of the crime the ballroom, hall, billiard room, study, lounge, kitchen, conservatory, library or dining room?
You have finished interviewing the suspects, examining the potential murder weapons and you have thoroughly searched the house.
Your suspects file into the drawing-room one by one. You, Inspector Grey, puff quietly on your pipe and look at the guests closely. A shiftier group of individuals you couldn't possibly imagine - motives abound, but only one of the suspects had motive, weapon, location and opportunity.
Taking a deep breath, you begin...murderer then weapon, then location.
You can validate your puzzle solution with certitude.