Showtime’s first new scripted series of 2013, “Ray Donovan,” has been a hit for the premium network, but it’s “Masters of Sex,” which debuts September 29th at 10pm after the return of “Homeland,” that looks even more promising. (Well, presuming Time Warner and Showtime’s parent company CBS settle their very expensive cold war in time for the channel to be restored to the subscribers currently being made to do without.) Lizzy Caplan and Michael Sheen play Virginia E. Johnson and William H. Masters, who together were pioneers of research into human sexuality at a time when scientific study of such a thing tended to be looked at as perversion. The show’s created by Michelle Ashford (“The Pacific”), and the trailer below combines hospital settings with some frank talk and imagery. Does it look like a potential hit?