Player 1 a $100 bill, and player 1 must hide it in one of the four boxes. player 2 does not observe where player 1 hides the $100 bill. once player 1 has hidden the bill, player 2 must open one (and only one) of the boxes. if the money is in the box that player 2 opens, then player 2 keeps the $100. if it is not, player 1 gets to keep the $100.