Lizzy Caplan and Michael Sheen in 'Masters of Sex'
Craig Blankenhorn/Showtime Lizzy Caplan and Michael Sheen in 'Masters of Sex'

"Masters of Sex," Showtime's new period drama starring Michael Sheen and Lizzy Caplan, premieres on Sunday, September 29th at 10pm, but you can watch the full first episode online right now.

Because the series, which is centered on real-life pioneers of the science of human sexuality William Masters (Sheen) and Virginia Johnson (Caplan), is about racier subject matter, the premiere isn't embeddable -- it's on YouTube, free, but behind a "Mature Content" wall. On the plus side, this means it isn't edited for content like some of the other Showtime online episodes have been.

Created by Michelle Ashford ("The Pacific"), the series looks at how Masters, a physician at the top of his field with an interest in an area of research that Washington University in St. Louis isn't exactly falling over itself to be associated with, meets and begins working with Johnson, a forward-thinking divorcee and mother of two he hires as an assistant. 

Watch the full first episode here.