The game begins with Lara's home exploding and burning down before a flashback to a week ago, showing Lara on the Mediterranean Sea, looking for Avalon. She had hoped to find out what had happened to her mother but instead she discovered Niflheim, a different Norse underworld, as well as one of Thor's gauntlets. She soon learns that Amanda Evert was on her trail and that she had captured Jacqueline Natla. By confronting Natla, Lara also learns that she needs to find Thor's Hammer to open the underworld where her mother is. Natla gives her a lead to begin her search, co-ordinates to the coast of Thailand.
With all of Thor's artefacts assembled, she plans to confront Natla; Zip had tracked her down to a ship on the Andaman Sea called Tisiphone, the sister ship to Amanda's 'Megaera'. With Alister's death still on her mind, she angrily questions her for the location of Helheim, and Natla provides it, telling her that she is the only one alive who knows the Ritual of Odin, which is needed in order to open the gates to the Underworld. Lara decides to free her on the condition that when she puts a foot wrong, she will kill her. Natla's co-ordinates point to the Arctic Sea, where Lara has to break a way through the ice. She finds her way to the gate of Helheim and watches on as Natla performs the ritual. Past the gates, she finds her mother, who had been turned into a thrall. Forcing herself to believe that her mother died long ago, she kills her. Natla appears after watching on and delightfully informs her that it was her who had killed Lara's father. She leaves, hoping that the Doppelganger would kill Lara, however Amanda saves her by using the power of her Wraith Stone to throw the Doppelganger over the rocky ledge.