When a trembling Mackenzie Phillips sat down on Oprah's couch, the former child star read a page from her upcoming memoir -- revealing that she had carried on an incestuous affair with her father, musician John Phillips, for ten years. Phillips tearfully described the drug-fueled sexual relationship, which began when she was only 17 and ended when she had an abortion in her late 20s. "My father was not a bad man," she told Winfrey. "He was kind of a testament to what drugs and alcohol -- in huge quantities -- can do to a person's priorities." Phillips said she went on the show because "I know that I can't be the only one this has happened to," and she knew that Oprah -- a survivor of incest -- would be sympathetic. To support her guest, Oprah brought out Phillips' One Day at a Time costar Valerie Bertinelli for a tearful reunion.