Captain Marvel [Billy Batson]; Mary Marvel [Mary Batson, aka Mary Bromfield] (Billy Batson's twin sister, introduction, origin); Sterling Morris; Percy Pill; Sarah Primm (Billy and Mary's nurse, death); Captain Marvel, Jr. [Freddy Freeman]; Shazam
Synopsis
Billy accidently discovers that a young girl, appearing on the Station W.H.I.Z. radio show, "The Mental Marvel Quiz," possesses half of a strange locket that he has the other half to, and that her former nurse confirms the fact that Billy and Mary are actually twins!