The Mouth of the Underworld, the eater of souls, has long been a subject of stories told to frighten Hautlyrun children. Its entrance has been lost for generations. Some believe it may never have existed.

But Kasuir and Jasryl have discovered a mysterious cave in highlands above Huispar. The Mouth of Underworld. They are certain.

They are forbidden to enter, warned that the old tales may in fact be true. But they do not believe those old stories. The old ways were all proven wrong when the Ven conquered and brought the railroad and modernity. They want to explore the cave, to prove that the Hautlyrun can be as scientific, as modern, as the Ven.

But sometimes old tales do have a kernel of truth. For something awaits them in the depths of the Mouth of the Underworld. From it, there will be no escape.