The Thief and the Innkeeper explained simply

A Thief hired a room at an inn, and stayed there some days on the look-out for something to steal. No opportunity, however, presented itself, till one day, when there was a festival to be celebrated, the Innkeeper appeared in a fine new coat and sat down before the door of the inn for an airing. The Thief no sooner set eyes upon the coat than he longed to get possession of it. There was no business doing, so he went and took a seat by the side of the Innkeeper, and began talking to him. They conversed together for some time, and then the Thief suddenly yawned and howled like a wolf. The Innkeeper asked him in some concern what ailed him. The Thief replied, "I will tell you about myself, sir, but first I must beg you to take charge of my clothes for me, for I intend to leave them with you. Why I have these fits of yawning I cannot tell: maybe they are sent as a punishment for my misdeeds; but, whatever the reason, the facts are that when I have yawned three times I become a ravening wolf and fly at men's throats." As he finished speaking he yawned a second time and howled again as before. The Innkeeper, believing every word he said, and terrified at the prospect of being confronted with a wolf, got up hastily and started to run indoors; but the Thief caught him by the coat and tried to stop him, crying, "Stay, sir, stay, and take charge of my clothes, or else I shall never see them again." As he spoke he opened his mouth and began to yawn for the third time. The Innkeeper, mad with the fear of being eaten by a wolf, slipped out of his coat, which remained in the other's hands, and bolted into the inn and locked the door behind him; and the Thief then quietly stole off with his spoil.