Roland Deschain and his ka-tet continue along the Path of the Beam toward the Dark Tower when their journey brings them to Calla Bryn Sturgis, a farming community living under a terrifying tradition.
Once every generation, mysterious raiders known as the Wolves descend on the Calla and take one child from each set of twins. The children eventually return, but they have been permanently changed. With the Wolves due to return, the people of the Calla ask Roland and his companions to help them fight back.
The ka-tet also meets Father Callahan, a former priest with a history of his own involving vampires and another world. His arrival connects Roland’s journey to events far beyond the Calla and introduces new questions about the forces surrounding the Dark Tower.
As Roland prepares the community for battle, Susannah faces a growing threat from within herself, and the ka-tet begins to realize that their journey may cross worlds in ways none of them expected.