Susannah Dean is pregnant, but another personality has taken control of her body. Mia, the mysterious demon-mother who shares Susannah’s mind, uses Black Thirteen to transport them to New York City in 1999, where she intends to give birth to the child they are carrying.
With the ka-tet separated, Jake, Oy, and Father Callahan set out to find Susannah. Meanwhile, Roland and Eddie travel to Maine in 1977, where they must protect a vacant lot in New York that is vital to the survival of the Dark Tower.
Their journey also leads Roland and Eddie to an unexpected encounter with a writer named Stephen King, whose connection to Roland’s world raises new questions about the nature of their quest.
As Susannah struggles against Mia and the remaining members of the ka-tet race to complete their separate missions, the path toward the Dark Tower moves closer to its final stage.