It is part of the Cosmere fictional universe and the third book of Sanderson's "Secret Projects" Kickstarter campaign.

Yumi is a yoki-hijo, a woman with the ability to call and bind spirits to do various tasks, attracting them by creating intricate stacks of rocks.

Concurrently in Kilahito, Yumi attempts to repel a particularly dangerous “stable” nightmare, who grows in strength while avoiding detection from Nikaro’s colleagues.

Yumi and Nikaro learn that the scholars' Machine demonstrated artificially powerful stone stacking abilities, effectively holding the world’s spirits hostage.

Meanwhile, Yumi confronts the Machine, stacking rocks so effectively that she is able to drain it of its energy and free the nightmares to die in peace.

Yumi dies, but Nikaro is seized by inspiration and spiritual energy, and he is able to bring her back to life through a masterpiece work of art.