Each player is dealt a certain number of hidden person cards. Consequently everyone knows some people who don't belong to the criminal ring. Each player must give these people an alibi if asked.
Everyone now has the task to find out through aimed guesses and clever deduction which person cards the other players have. Whoever knows that first, can expose the three criminals first.
2. The dealer deals
The dealer shuffles the 27 person cards (red backs); the player on his right cuts the deck.
First, the dealer puts aside the three uppermost cards. These three cards represent the three members of the criminal ring "Black Vienna".
Then he deals (face-down) the remaining 24 person cards, starting with the player to his left. With three players each receives eight cards, with four each receives six, and with six each receives four. If five players participate, the dealer receives four cards, the other players five.
Each player now has secret information in her hand. Each player knows that the persons represented on his cards are not the sought criminals. He must give them an alibi, if asked.
Each player can make notes on his investigation sheet, marking the cards that he possesses under his name with plus-signs (+), and under his opponents with minus-signs (-). Everyone must hide their investigation sheet during the game.
Each player can of course mark his sheet as he wishes to best assist him in recording the results of investigations and to make deductions.
3. Investigations and answers
The dealer begins the investigation. He takes one of the three face up investigation cards and places it in front of any other player. He thereby asks this player to provide an alibi for any or all of the suspects shown on the card.
The player who has been questioned then places one chip on the card for each matching suspect card he holds in his hand; if he holds no listed suspects, he places no chips. Thus if a player received the card "BLM" and he had "B" in his hand but not "L" or "M", he must put exactly one chip on the card.
The investigation card, on which now lie zero to three chips, remains down before the interviewee, and he now asks the next question.
Thus, the game continues. The player asked a question always gets to ask the next question.
4. Special investigations
Once each player has been questioned at least once and at least six investigation cards have been played, special investigations may be performed.
Whoever is asking a question may also take an investigation card in front of another player but with no chips on it, and place both it and an investigation card drawn normally in front of the player he's chosen. That player must respond to each of these cards as instructed in #3 above. (Translator's note: when trying to sort out the rules for the game, I interpreted this rule differently - offering players a choice of a normal or special investigation. Looking through the rules again, I think the above is the actual rule; I have no idea whether the misinterpretation makes for a better game or not. But anyone who directly or indirectly learned the game from Aaron Fuegi or I is likely to have played by my misinterpretation.)
Each player marks the results of the investigations into his investigation sheet under the name of the interviewee and constantly supplements it through clever deduction. Plus-signs are recommended (+) as well as minus-signs (-) when certain a player has or doesn't have a certain card.
The goal of the deductions is to find what person cards other players have.
Because whoever first knows which person cards the other players have, knows for a fact the three members of the criminal ring "Black Vienna".
(Translator's note: of course, it's not necessary to know which cards any other player has to be certain of the makeup of the criminal ring...)
Whoever believes they know the three members of the criminal ring knocks on the table and says "Black Vienna".
Each player can do this at any time, whether or not they were involved in the latest investigation.
At this point the game is interrupted. The player who has knocked makes an accusation. He marks the initial letters of the three persons who in his opinion belong to the criminal ring with three clear circles on his investigation sheet. Then, he covers his investigation sheet, looks at the three criminal ring cards, and checks whether his accusation is correct or not.
If the accusation was not correct, then the game continues. The player who made the wrong accusation still plays along, however he obviously may raise no second accusation. His scored for this game is zero.
7. Game end
If the accusation is correct, however, the game is over. The successful accuser has won the game and receives three points for each chip left in the middle. Now the other players who have made no accusation may circle the initial letters of the three people who they believe belong to the criminal ring on their investigation sheets.
The three criminal cards are then uncovered visibly for everyone, and each player who has the three criminal ring members correct receives one point for each chip left in the middle. All other players receive zero points.
8. Unsuccessful investigation
If all players have accused incorrectly save one, the game is broken off. This one player may ask one final question, and then must make an accusation. In this case, this player receives one point per remaining chip if successful, zero otherwise.
If three chips or fewer remain the game is also broken off. All players receive zero points.
Second, here is a suggestion for how to handle players who have made incorrect guesses. I suggest that these players not be allowed to ask questions and should only answer them. The following is the fairest method I have come up with for handling this. Wait until the first time a question is asked of a player who has previously made an incorrect guess. After that question is answered, choose a random player among the others to ask the next question (call this a free question). The next time this situation comes up, the next player (skipping players who have made previous incorrect guesses) clockwise around the table from the last person to ask a free question gets to ask this free question.