Susannah-Mio, Divided Girl of Mine

Susannah Dean, her body taken over by a demon-mother named Mia, has used the power of Black Thirteen to transport out of Calla Bryn Sturgis to New York City in the summer of 1999, so that she can give birth to her "chap". While Jake, Father Callahan, and Oy try to break Susannah's date with destiny at the Dixie Pig on Lexington and 63rd, Roland and Eddie use "the persistence of magic" to get to East Stoneham, Maine in the summer of 1977. It is a frightful world at they walk in on. For one thing, it is real, and the bullets are flying. For another, it is inhabited by the author of a novel called Salem's Lot, a writer who turns out to be as shocked by them as they are by him.

Just who is Mia, and more importantly, who (or what) is her chap?