This is a team-based co-operative challenge. The team/patrol must solve the puzzle within the time period. It was designed as one zone within an indoor crystal maze night but can be equally done as a stand-alone activity.
2 opaque boxes (can also be done with two doors that are closed but near to each other)
The team is presented with two closed boxes. In one box is a prize, in the other is a fast acting poisonous gas (in reality it's empty but it adds to the story)
The team may open one box and one box only.
They are told that one guardian will always tell the truth and the other will always lie. They are not told which is which.
They must ask just one guardian only one question and then choose a box.
They may not touch the boxes.
They have three minutes to solve the puzzle.
Solution: Ask “If I ask the other leader which box has the crystal in, which one will they tell me?” and then choose the other box. The guardian they ask will always tell them the poison box because either they are the liar or they know the other guardian will lie to them.