An old gentleman whose eyesight was failing came to stay in a hotel room with a bottle of wine in each hand. On the wall there was a fly which he took for a nail. So the moment he hung them on, the bottles fell broken and the wine spilt all over the floor. When a waitress discovered what had happened, she showed deep sympathy for him and decided to do him a favour.
So the next morning when he was out taking a walk in the roof garden, she hammered a nail exactly where the fly had stayed.
Now the old man entered his room. The smell of the spilt wine reminded him of the accident. When he looked up at the wall, he found the fly was there again! He walked to it carefully adn slapped it with all his strength. On hearing a loud cry, the kind-hearted waitress rushed in. To her great surprise, the poor old man was there sitting on the floor, his teeth clenched and his right hand bleeding!