The magician reminds the audience of Murphy´s law, that if something can go wrong it will. For example, the magician continues, when you want to open a door or a drawer, the key that will open the lock will always be the last one you try. Why?, who knows, just Murphy´s law in action. To demonstrate this principle, the magician shows a fancy wooden chest and five keys. He lets a spectator use one of the keys in order to show that this one opens the chest, and proceeds to mix that key along with the other 4 in a transparent glass tumbler. Then, four spectators each freely select a key, leaving only one in the glass. Each spectator tries his or her key, and they discover that their keys don´t open the chest. Finally the last spectator tries the last key only to find that this one is the right one. Everything can be examined.