The story actually begins with Loki borrowing Frigga' s falcon coat, and flying out into Jotunheim. Out of curiosity Loki lands on a window ledge at the Giant Geirrod' s hall to peer in. Geirrod notices this odd " bird " and orders a messenger to capture the strange creature. Loki, confident that he is safe, waits until his pursuer climbs almost to the spot he is sitting before attempting to fly away. Unfortunately for Loki he waited a slit second too long, and was captured just as he spread his falco wings to fly away. When Loki was brought before Geirrod, the Jotun could tell by the eyes of the creature that it was not a bird, but was in fact a man. He demanded that Loki tell him who he was, and what he was doing outside his window. Loki kept quiet however which infuriated the Jotun. Geirrod then locked Loki in a chest for three months without food or water, as punishment. When Geirrod released Loki and demanded he speak, this time Loki told the Jotun everything. Loki promised the Giant that if he were released he would trick Thor into coming to Geirrrod' s stronghold without his hammer, or his belt of strength.
The story unfortunately does not tell us how Loki tricked Thor to journey to Jotunheim without his belt of strength or mighty hammer, but it does tell us that on his way he stayed with a Giantess named Grid, who was the mother of Vidar the Silent. When Thor mentioned to Grid where he was going the Giantess told Thor the truth about Geirrod. She warned Thor that the Jotun was as sly as a fox, and could be a very dangerous enemy. Grid helped Thor by lending him her belt of strength, ( I guess they were common ), and her iron gloves. She also gave to Thor her staff to aid him on his journey through Jotunheim. This staff is known as Grid' s stick.
Thor then left Grid' s home and came upon a large river called the Vimur. The current was strong so he put on the belt of strength Grid had given him, and braced himself as he crossed the torrent by using Grid' s stick for support. By midstream the water had risen so high that it was breaking over his shoulders. Thor then called out to the river as though it were alive : " Vimur do not wax now, I happen to be wading through you on my way to Jotunheim. You know that if you do, so will my strength divine until it reaches up as high as heaven. "
Thor then looked ahead up a rocky ravine and saw Geirrod' s daughter Gjalp squatting over the river making water. Seeing that it was Gjalp who was causing the river to rise, Thor reached down and picked up a large rock, and with all his might threw it at the Giantess. As he let the rock go Thor shouted in anger at the Giantess : " A river must be dammed at its fountain-head . " Thor, as always was the case, hit what he aimed at and Gjalp was knocked down off of the banks over the river. As the river receded Thor was carried near the shore where a lone rowan tree stood on the bank. Thor caught hold of one of the branches and was able to pull himself ashore to safety.
Tomorrow : Thor battles with Geirrod !
Go with Odin' s wisdom, Freyja' s love, and Thor's protection !