Sleuth Publications Ltd, 1981, any number of players, and pretty much any age. In Consulting Detective, players tackle the case books of that most legendary of detectives, Sherlock Holmes. In short, the game is a foot! Er, no, that's not it. I mean, the game is afoot!
I've never read the actual A.C. Doyle stories, but my understanding is that the cases in CD are not culled directly from them. However, they were definitely conceived and written in the same basic spirit.
The game comes with a casebook, a map of London, and various "reference" pamphlets (directories of homes and businesses, newspaper clippings, etc). The game can be played any number of ways (solo, collaboratively or with players divided up into teams), but we generally prefer to solve the cases as a group.
Each case starts in traditional Holmesian fashion - IE, some distressed soul shows up at 221B Baker Street begging for Sherlock's assistance. The crime is then introduced and discussed in short story fashion. During the course of said narrative, Holmes inevitably comes up with some convenient excuse to bugger off - thus leaving the case in the hands of the players (now the Baker Street irregulars). The players then decide where they want to go first - the scene of the crime? The morgue? The coroner? The old Bailey? Or perhaps off to visit one of the various personages mentioned during the introduction of the crime? Once a location is decided upon, you look it up in the directory and then see if there is a corresponding entry in the clue book (and unless yours is a really inept group of sleuths, there usually is). Each location in the clue book will have a brief narrative telling you who you met there, what they had to say, and what you observed - hopefully providing the group with further avenues of investigation, and ultimately allowing you to unwravel all of the twists and turns of the crime(s) (there usually being several interconnecting mysteries to be solved within the main one).
Once you've decided you've solved the mystery, you then take a little test to determine your score (subtracting points for each place you had to visit). Lastly, you read Sherlock's solution to the case and see how well you did as compared to the great detective (and don't fret if you come up short - Holmes's abilities in this game are way beyond superhuman).
Hitherto, our group had never played anything like this before, and suffice it to say, we think it's an absolute blast. The group dynamic you get playing CD is just completely different from traditional boardgame play. We really get swept up in trying to put the pieces of the puzzle together - excitedly bouncing ideas off each other about who done what to whom (along with the equally important wheres, whens and whys). Naturally everyone has their own pet theories, so the question of "who should we go interrogate next?" inevitably becomes a bone of contention.
The mechanic of visiting different locations and gathering bits and pieces of information is well conceived, and the various short narratives are entertaining and well written. Honestly, we actually find ourselves firing ad-hoc questions at the clue-reader-guy (as if the characters were really there and able to answer them). Overall, a very unique, entertaining and well-made game (and from what I'm told, still highly regarded and hotly sought after).
On the downside, the base game (long out of print) comes with just 10 cases - and once you've done them, well, you're done. There are add-on cases as well, although quite difficult to find nowadays. The add-on sets that I know of are The Mansion Murders, The Queen's Park Affair, West End Adventures, and Adventures By Gaslight (possibly also something called "East End Murders", but that might be vaporware). Unfortunately, our experience with the add-ons is that they're (for the most part) a bit overdone. Unlike the base game (where the cases are relatively concise and can be solved in a single session), the cases in the add-on sets tend to be overly bloated and usually take multiple sessions to slog through. And when you only get together once a month, trying to remember all of the details between sessions becomes difficult (to say the least). Quite frankly, we wish they'd have just stuck with the original paradigm.
The base game was originally published in binder form, but was later re-issued in "boxed up" form. As near as I can tell, any actual differences in content between the two releases are trivial.