Having realized her feelings for Loki, Sigyn is looking forward to spending more time with him while exploring the world of the giants in Jotunheimr. However, their trip goes awry when Thor's hammer is stolen by the giant Thrym who will only return it in exchange for a goddess as his bride.

To retrieve the weapon, they'll use Loki's specialty: shape-shifting. Thor, transformed into a goddess, with Sigyn and Loki as handmaidens, promise Thrym a royal wedding as a ruse to infiltrate his kingdom and locate the hammer.

However, as the date of the wedding nears and the hammer remains elusive, Sigyn finds she has something else to contend with: a vicious water spirit lurking in the underground sea that she might have more in common with than she wants to admit.