The lightening

It was raining cats and dogs and four people were
 taking shelter under a small roof that was in a dilapidated condition. One
 of them felt that they would all perish in this rain if among them there is
 a wicked person. This he expressed openly and suggested that each of them
 should go out, touch a green tree in the distance and return to the shelter
 so that the person if wicked would be burnt since lightening strikes a
 green tree only first. This way three of them touched the tree and returned
 and nothing happened to them. They thought that they were all good and the
 last one is the wicked. They anxiously awaited the event of his getting
 burnt when he left to touch the tree. The lightning struck this time,
 however not the tree, but the shelter, making it clear that the last one was
 the only good person who saved all the other three contrary to their belief.