“King of Shadows,” a new play by Roberto Aguirre-Sacasa, will preem Off Broadway this fall in a production from Working Theater.Plot centers on a 15-year-old runaway who claims he’s being chased by demons and the social worker who takes him in. Working Theater a.d. Connie Grappo (“Tabletop”) directs. Aguirre-Sacasa’s recent Off Broadway productions include “Good Boys and True” at Second Stage and “Based on a Totally True Story” at Manhattan Theater Club. He also is a writer on HBO skein “Big Love,” as well as a scribe at Marvel Comics. Cast of “Shadows” includes Satya Bhabha (“Rafta Rafta”), Kat Foster, Sarah Lord and Richard Short. Production begins previews Sept. 2 ahead of a Sept. 7 opening at Theater for the New City.