In an Entertainment Tonight exclusive, the sister of the other woman in the John Edwards' scandal sits down with our Thea Andrews for her only interview, following Edwards' explosive admission he had an affair with Rielle Hunter and reports claiming that he had allegedly fathered her infant daughter.

Watch our new extended preview of Rielle's sister, Roxanne Druck Marshall, as she apologizes to Elizabeth Edwards for her sister's behavior, and admits that she feels "ashamed."

Then, watch Wednesday's ET for more of our in depth interview as Roxanne gives a sister's account of the affair that devastated a family and rocked a country; personal insights into the woman at the center of the scandal and new alleged details of when and how the affair began; and who her sister's baby looks like. Edwards claims his affair with Rielle was a brief encounter, but Roxanne Druck Marshall tells a different story to Entertainment Tonight in what promises to be one of our most talked about interviews of the summer.