Time passed. The gods, thinking that Idun had accompanied her husband and would soon return, at first paid no heed to her departure, but little by little the beneficial effect of their last apple feast passed away. They gradually felt themselves grow old and stiff, and saw their youth and beauty disappear; so they became alarmed and began to search for the missing goddess of perpetual youth.
Close investigation very soon revealed the fact that she had last been seen in Loki’s company, and when Odin sternly called him to account, this god was forced to reveal that he had betrayed her into the storm giant’s power.
“By his mocking, scornful mien,
Soon in Valhal it was seen
’Twas the traitor Loki’s art
Which had led Idun apart
To gloomy tower
And Jötun power.”
Valhalla (J. C. Jones).
The gods now indignantly bade Loki undo the harm he had done and immediately bring the goddess back, warning him that unless he complied with this command he would forfeit his life.