From Recapped.com:

Ruth Wilson is naked during a sex scene about half way through the episode. However, you only see glimpses of Ruth’s breasts. Ruth is nude during another sex scene at the end of the episode but she doesn’t really show anything.

http://www.recapped.com/celebrity-nudity-rumors-november-1-2014

The Affair airs on Showtime tonight at 10PM.

 

The Affair S01E04 (Ruth Wilson-Brief Breasts)