The sun grows black, the earth sinks into the sea. The bright stars vanish from the heavens. This is the final destiny of the gods, when the world will fall to ruin. Before she was a hideous monster, the Queen of the Underworld was simply Hel. But cast as a young girl from lofty Asgard, the realm of the gods, by Odin the Allfather, Hel's fate as the terrible goddess of death is sealed. Half beauty, half crone, she has reigned for centuries over the starless darkness of Niflheim, welcoming the most pitiful amongst death's travellers to her icy prison. Until, one day, a memory shifts, and she is forced to seek out the sun in Midgard, where humans have made their home. Faced with a terminal cancer diagnosis, Helen Firth makes the impulsive decision to uproot her quiet life as a librarian and move to her childhood town in Orkney after forty years, to make peace with her past and ultimately die.

Under the wintering solstice sun, she reconnects with the ungainly but affable Thorfinn Coffin, who helps her address the real reason she has chosen to return to the island. As Helen nears ever closer to death, and ever closer to Thorfinn, Hel in turn finds herself drawn to Helen. She, too, has a past to confront and a lesson to learn - that perhaps who she thinks she is isn't who she's really meant to be.