Since we have all marked our calendars for the return ofMasters of Sexin September, the one thing I was most waiting for was to learn who will guest star this season, and today we know the answer. Niecy Nash and Betty Gilpin will be joining the show for the 4th season.

While we won’t know what their characters and story arcs will truly look like until the start of the new season, Deadline Hollywood gave us a little peek into their characters and how they will fit into the show:

Nash will playLouise Bell, a local AA chairperson running Masters’ court-ordered daily meetings.She fervently believes in AA’s message, and uses it to push Masters to reevaluate his life.Gilpin will play Nancy, a former medical student of Barton’s (Beau Bridges) who partners with Masters, adding a second MD to the practice.

Most of us know Betty Gilpin from Nurse Jackie,where she bared her breasts a few times, so I think it’s a safe to say that we will get a glimpse of Betty Gilpin topless again. Maybe even more than once. When it comes toNiecy Nash, your guess is as good as mine as far aswhether or not she’ll get nude. But with Masters of Sex, you never know who wants to get topless.

Masters of Sex returns Sunday, September 11th at 10 p.m.on Showtime.