Thor wakes up one morning to find that all is not right with the world. His magical hammer, Mjollnir, is missing.
Convinced that the theft is just one of Loki's usual pranks, he finds the trickster god and demands to know where his hammer is.
Loki insists he didn't take Thor's hammer. He's pretty sure he knows who did, though, and he has a plan.
Thor asks Freyja if Loki can borrow her ride. It's a magical feather dress that gives the wearer the wings of a bird. With some interesting whirring noises, Loki departs for Jotunheim, the land of the giants (called Jotun).
In Jotunheim, Loki finds the frost-giant Thrym sitting on a mound braiding golden leashes for his dogs and stroking the manes of his horses in a creepy sort of way.
When Loki tells Thrym that Thor's hammer is missing, the giant admits to hiding it eight miles below the earth. In exchange for returning the hammer, Thrym explains, he wants Freyja, the most beautiful goddess in Asgard (the land of the Aesir gods), for his wife.
Loki flies back to Asgard and breaks the bad news to Thor.
Right away, Thor insists on finding Freyja. He tells her to put on a wedding dress. She's got to marry Thrym.
Freyja is totally offended that Thor would even suggest such a thing (she even snorts).
All the gods hold a council to discuss how they're going to get Thor's hammer back.
The watchman god, Heimdall, suggests that Thor put on a wedding dress, some gemstones, Freyja's special necklace, and some keys. In other words, Thor should dress up as Freyja and travel to Jotunheim to get his hammer back himself.
Thor's not thrilled about that plan. He's sure that all the gods will call him un-manly if he does that.
Loki tells Thor to suck it up. If he doesn't get his hammer back from the giants, they'll use it to take over Asgard.
Reluctantly, Thor allows the gods to dress him in a wedding gown and deck him out with gemstones, keys that rattle, and Freyja's special necklace, Brisingamen.
Loki decides that he'll go with Thor to Jotunheim as a bridesmaid.
Thor calls for his goat-driven chariot. After much thunder and lightning, Loki and Thor arrive in Jotunheim.
When Thrym sees them coming, he instructs his servants to deck the halls, for Freyja's on her way to marry him.
Thrym brags about all the shiny cows and gemstones he owns, and muses that, now that he has Freyja, he's got everything a giant could ever want.
Fast-forward to the wedding feast: Thor eats an entire ox, eight salmon, three barrels of mead (basically beer), and the entire wedding cake.
Thrym's totally impressed, and a little bit surprised, since he's never seen a woman eat so much.
Loki excuses the "bride's" monstrous appetite to Thrym by explaining that she was so excited about her marriage to him that she fasted for eight days in a row.
Eager to kiss his bride, Thrym lifts her veil and immediately leaps back in horror. His bride's eyes, he says, are fiery red!
Loki explains that the bride's been so excited about her marriage to Thrym that she hasn't slept for eight days straight.
Thrym's sister appears in front of "Freyja," demanding the bridal fee, a payment the bride and her family owe the man who marries her. She tells "Freyja" to take the rings off her fingers.
Now it's time for Thrym to fulfill his side of the bargain. He instructs his servants to bring in Thor's hammer, Mjollnir, and lay it in the bride's lap to "bless" her.
Thor's heart leaps in his chest when he sees his hammer placed in front of him. Immediately picking it up, he kills Thrym and the giant's entire household.
Instead of a bridal fee in shillings, Thrym's sister gets smashed in the head.