Human Clue

Have six people dress up as the six characters from the board game Clue (a whodunit game where the players have to guess the culprit, murder weapon and the room where the deed was done).
Work out a plot, so that participants can listen in on conversations from the characters which give clues away.
Plant the actual murder weapon somewhere (as well as some false ones!) – e.g., a knife covered with tomato sauce hidden in a sink. Have other clues planted around the rooms, or even on the bottom of shoes, back of jackets etc.
The youth groupers have to wander around all of the rooms, listen, observe, look for physical clues, and at the end of a set period of time guess the murderer, the room and the weapon (perhaps the motive too).