Loki and Odin have just traveled through Midgard and are now in Jotunheim. They are both famished from their voyage and they find no food until Loki finds a cow.
Loki slaughters the cow and cooks the meat in strips but every time he cooks it through it is raw by the time he gives it to Odin who laughs at the whole situation. Loki vows to cook the meat. Odin then leaves and an eagle appears with a deal that he will help cook the meat in exchange for his share. The eagle deceives Loki and kidnaps him.
the Eagle carries Loki to a cave where he informs him that he will never leave until he agrees to get some of Iduna's apples for him. Loki agrees.
ell the gods and goddesses in Asgard have received their apple form Iduna and have left with the immortality bestowed on them. Loki has stayed behind to talk with Iduna and he deceives her into leaving Asgard with promises of better apples.
While Iduna is outside of the Asgardian wall she is scooped off the ground by the giant in the form of an eagle. it happens to be iduna has apples with her. Iduna is taken to the cave and is kept their even though she never give the giant an apple. Without Iduna the gods and goddesses are all aging.
Thor is realizing that everyone is aging without the apples and knows that Loki probably played a part so he threatens Loki who then goes and makes himself a captive of the giant's daughter as a falcon and then spies on the situation.