A year after Katla's eruption, the shattered survivors are still grappling with the aftermath. Suddenly, an ash-caked woman appears on the glacier.

Emerging from the shadows, a surprise visitor gets Gríma's full attention. As the ground beneath them shifts, Darri and Gunhild heed Katla's call.

The cold, cruel reality of life in Vík í Mýrdal comes home to Gríma. Darri studies his strange discovery in secret. Gunhild confronts the newcomer.

What's real, what isn't — and does it matter? The truth comes out, the fear grows and the mystery threatens to sweep away everything before it.