Thor, the God of Thunder, had been feeling a bit tired and lazy recently. When he was in this mood, humans down on Earth enjoyed peaceful, storm-free weather. During the past few weeks, Thor had picked up his mighty hammer only once to pound the skies, and even then he hadn't really been too keen to shake the heavens as he usually did.
The other gods and goddesses in Valhalla were getting a bit concerned about Thor's apathy. Something had to be done as quickly as possible to snap him out of his present grump, and get him swinging his hammer again.
Odin, King of the Gods, was well aware of the situation with Thor, and one morning during breakfast, he told the God of Thunder to get his act together or there would be severe consequences.
Thor felt very guilty about letting the other gods down, and resolved to make immediate amends for his recent poor performance as God of Thunder. He gulped down a last mouthful of breakfast, and stomped off to get his hammer.
But it wasn't where he usually kept it. Thor searched in all the halls of Valhalla, under beds, behind curtains and on the top of cupboards. But the hammer was missing. The other gods joined Thor in the search, but it was all a waste of time. Thor's mighty hammer was nowhere to be found.
Odin immediately called an emergency meeting. 'It is obvious that Thor's thunder-hammer has been stolen from Valhalla,' the King of the Gods announced gravely. 'And the only creatures who would do such a deed are the Giants. I propose to send Loki into the Realm of the Giants to investigate.'