Isabella came to town as a favor to Michael Baldwin to help break up the already shaky marriage of Paul and Christine Williams. Michael wanted Christine for himself. Isabella went to Paul as a damsel in distress, in hiding and afraid of her ex-husband who was in prison. Paul took the case and she ended up living in his apartment to be safe. Paul became more and more drawn to Isabella, but insisted they keep their distance while she was his client. During his investigation, Paul found documents that proved James was guilty, and he was brought to justice for his crimes. But Paul also discovered that Isabella did more than just the books for her husband's business when he found Isabella among the photos in a book of prostitutes for hire. Paul confronted her about it, she admitted it was true, but Paul forgave her.
Isabella kept trying to leave town, but either Michael or Paul would give her another reason to stay. She ended up pregnant with Paul's child, after one night in his bed. That same night Christine decided to return to Genoa City and work on their broken marriage, and walked in on them kissing passionately in the living room. Instead Christine crept back out, and filed for divorce.
Isabella didn't want to tell Paul that she was pregnant because she felt that he was too hung up on Chris, so she had a brief affair with Michael and told him that he was the father. Michael was outraged at first, even drew up legal papers for her sign. But Isabella has something on Michael from the past, so he backed down and went along with her demands of rent, baby furniture, and everything she needed to live until the baby was born. Michael also arranged for a job for her in another town for after the birth. Just as Michael was softening to the idea of a child and a future with Isabella, and Paul was getting involved with former wife Lauren Fenmore, Paul found out about the baby's paternity and wanted to be a father to the child. With this major lie Isabella fell out of grace with both Michael and Mary.
Paul moved in with Isabella and continued to use her manipulating ways to keep him under her thumb as tightly as possible. Paul's mother, Mary, went to great lengths to try to convince him that Isabella was all wrong for him and would ruin his life, and tried to convince Isabella to go away to a home for unwed mothers. All despite the fact that Isabella was providing Mary with the grandchild, and Paul with the child, they both had always wanted. Mary even begged for help from unlikely sources in Lauren, Christine, and even Michael -- all of whom she disapproved of as well, but had had no luck at all. But Paul moved out on his own volition when Isabella started pressuring him to get married. Their baby boy, Ricardo Carl Williams, was born, but unlike Isabella's delusions, Paul was not willing to become one happy family with her. Complicating things was the sudden return of Christine, who rebuffed him for the baby's sake, although she still had feelings for Paul. Paul's response was to marry and move in with Isabella.
Christine spent long hours working with Michael Baldwin and accepted Michael's marriage proposal. Paul invited Isabella's estranged father Ricardo to Ricky's christening, and they happily reunited. Michael showed up, asked Ricardo not to mention that they knew each other or Isabella's past, then announced his and Christine's engagement, much to Paul's rage. Paul attacked Michael, who left with a black eye. Later Paul showed up at Chris's apartment and forced himself on her. The next morning Christine disappeared, leaving both Michael and Paul wondering. Chris was gone for months when the guilt got to Paul, and he told Isabella that he and Chris had sex that night. Isabella left him, only returning occasionally to see Ricky.
Chris returned in disguise as the dark-haired mysterious Kelly Simmons, bent on getting the goods on Isabella. Paul saw through Chris' disguise, and they came to an understanding about the "rape", but Paul chose Isabella and his son. Paul took Ricky to Isabella's parents in Los Angeles, leaving Isabella to finish packing for their move to L.A. Just before Michael and Chris were to be married, Michael confessed to Chris that he set up Isabella to meet Paul so Chris and Paul would split up for good, then Michael could have Chris. Chris exploded, walked out on Michael, and flew to L.A. to tell Paul the whole story. She found Paul camping on a beach, told him the truth, and they ended up making love in the sand. Upon their return to Genoa City, Paul moved back into their former apartment with Chris, while Isabella plotted revenge.
One night Isabella called her only friend Diane Jenkins who was with Michael, telling them that someone was breaking in, then she screamed. When Michael arrived he found what appeared to be a bloody murder scene and Isabella missing. Christine woke up unconscious in her car in the woods and told Michael and Paul of her only memory -- Isabella screaming not to hurt her, of blood, and a boat. Michael tracked down the boat, which was covered in blood, and destroyed the evidence against Chris. The night before Chris was to be arrested for Isabella's murder, she was attacked in her bathtub by a very much alive Isabella who had drugged her wine. While wielding a butcher knife, Isabella told Christine how she had set her up. Paul arrived in the nick of time, slugged and knocked out Isabella. As he was reviving the nearly drowned Christine, Michael arrived and saved them both from the crazed Isabella. The police arrived and hauled Isabella away. She was committed to a mental hospital, and Paul and Chris were free to be together once again, but Paul was having issues dealing with "the rape" so they never did. Ricky apparently spent his entire childhood with Isabella's parents in Los Angeles with Paul rarely visiting and calling him.
In July 2012, Isabella's son Ricky had turned out to be a killer, several times over, and Paul had to shoot and kill him when he discovered Ricky about to kill Eden with a butcher knife. Afterward, Paul and his daughter Heather cried and hugged. Heather warned Paul that he could not leave, but later Paul slipped away, ended up at the sanitarium in Los Angles to see Isabella, and told her what had happened to their son. But Isabella sat with her back to Paul, brushing her hair and humming, and did not respond.