Sonni Carrera, Josh Lewis's first wife, was a brilliant psychiatrist in Venezuela and, after a whirlwind courtship, the pair married. Unfortunately, on their honeymoon, Sonni fell off a cliff to her death or so Josh thought. Somehow, Sonni survived and, in 1987, found her way back to Josh after Josh and Reva had just broken up. Shocked at seeing his wife again, Josh's feelings for her came to the forefront and he remarried her.

However, things weren't as innocent as they appeared. Soon after the wedding, Sonni started having an affair with Josh's best friend, Will Jeffries, who kept calling her Solita. Apparently the pair were lovers as teenagers and together they formulated a plan: they would murder Josh and collect his estate. However, Reva discovered Sonni's affair with Will and took photographs of them together but didn't show Josh. She did tell him, however, that she had seen them together. Josh rushed to Will's apartment and found Sonni with Will, but believed that it was all very innocent. Later, Sonni became more and more reluctant to go ahead with the plan and finally begged Will to forget about killing Josh. Unfortunately, Will wasn't about to lose his payload. In February 1988, Will set Josh up to drive off a bridge but Reva was nearby and jumped into the ice water to save him.

Josh survived but Reva suffered a cardiac arrest. Josh felt very guilty about this which made a pregnant Sonni furious since she was beginning to develop real feelings for Josh. Sonni went to Reva's room at the hospital and considered killing her but didn't have the heart to do it. Instead, she ended up saving Reva's life as she was choking on an air tube. About this time, Sonni's father, Welles Carrera, arrived in town and threatened to tell Josh the truth---Sonni had committed suicide as a teenager; this woman was his rebellious daughter, Solita--Sonni's twin sister., Will arranged for Carrera to die in a car accident but didn't tell Sonni that it his fault. Sonni later lost her baby because of a fight with a recovered Reva. When Will learned that the baby wasn't his but Josh's, he angrily confronted her. During the course of the argument, Sonni knocked Will out in self-defense. Convinced that she'd killed him, she put his lifeless body into his boat and set it adrift.

However, to Sonni's shock, Will wasn't dead after all. When an amnesiac Will showed up again in Springfield, he got involved with Mindy Lewis. Meanwhile, Ed Bauer hired Sonni at Cedars as a psychiatrist and her first patient was Will. Soon, she began to toy with his mind. When she realized that Will was getting his memory back, she suppressed his memory of the accident and drugged him. In the meantime, Reva finally showed Josh the picture of his wife and Will in a tight embrace, and together they went to Venezuela to investigate Sonni's past. There, they met up with Sonni and Will and figured out the criminal lovers' master plan. Thinking fast, not realizing that his memory had returned, Sonni planted the following suggestion in Will's mind: Will was to tell the Venezuela police that Josh, not Sonni, had tried to kill him. In early November 1988, Josh was arrested for trying to kill Will, just as Will let Sonni know his memory had returned. Later, Reva got Will alone in a hotel room and extracted an anguished confession from him which she got on tape. Then, Alan Spaulding showed up to throw his usual monkey wrench into the proceedings by becoming Sonni's lover and co-conspirator.

Later, Josh confronted them with his shocking discovery that Sonni was not Solita after all, but Sonni herself! Frantic that things were unspooling in her plot to take control of Josh and Spaulding Enterprises, Sonni fired a gun and Alan caught the bullet, which left him paralyzed. Meanwhile, in the last week of November 1988, with Josh separated from Reva -- the fully recovered Will kidnapped Reva and brought her to the same abandoned Carrera house where Sonni was holding Alan. Will injected Alan with a needle, while Sonni knocked out Reva and prepared to inject her as well! Luckily for Alan and Reva, Josh discovered a hastily written note from Reva, about her suspicions about Will and Sonni and Josh, with Reva's brother, Rusty, rescued Alan and Reva in the knick of time. As for Will, he disappeared while Sonni was arrested and sent back to Springfield to face a trial.

In January 1989, Sonni stood trial for the still missing Will's attempted murder. When Sonni's inconsistent testimony left everyone baffled, Reva and Rusty investigated her past in Venezuela and found her twin sister Solita's remains in a grave, at a monastery, near the now run down and abandoned Carrera ranch. They wrongly presumed that Sonni had killed Solita and taken on her personality as an alter ego.! Back in Springfield Will made his reappearance, while Sonni finally unraveled and lost her "Solita" persona. Will, disguised as a monk, took Sonni down to Venezuela when he became concerned that Reva and Rusty were about to discover their duplicitous schemes . A confused Sonni woke up at the Carrera ranch and, not realizing that Reva was inside still investigating Solita's death, set fire and burned down the place. Luckily Rusty, sensing that Reva's life was in danger, saved his sister in the nick of time. Unfortunately, Reva separated from Rusty when she decided to confront Sonni. Meanwhile, Sonni, not knowing where Will was, briefly held Will's mother ,Anita Ybarra, hostage at gunpoint -- trying to find out more about her past with Will.

Finally, Reva caught up with Sonni as she was about to repeat the accident that nearly killed her in October 1986, by flinging herself off a suspension bridge. Reva got Sonni to finally remember what happened the day her sister, Solita died: When Sonni was a teenager, she had an affair with Will. When her father discovered them together, he assumed that she was Solita. Wells savagely whipped his daughter with a belt. Unfortunately, his anger wasn't satisfied and when Solita came home she too was beaten by Welles, while Sonni -- protected by Anita Ybarra – watched in agony. Solita then killed herself by hanging herself in the nearby monastery. At that point, a guilty Sonni took on the personality of her now deceased twin as a defense mechanism. After her confession, Reva got Sonni to walk away from the bridge, only to have it collapse. Luckily, Josh and Rusty saved both Reva and Sonni in the knick of time. Rusty then arrested Will and all of them returned to Springfield. Sonni spent about two months in an institution but made such a fine recovery that Ed rehired her at Cedars. Will was another matter. Ed fired him when he admitted he that he had tampered with Marah's paternity tests.

Will would continue to be a thorn in the side of Reva, Josh and their respective families, the Shaynes and the Lewises. In April of 1989, Will kidnapped Marah and left the child in the care of his mentally unbalanced mother, Anita Ybarra. In an effort to win back his wife, Mindy Lewis, Will planned to play hero and "save" the child so that a grateful Josh would tell him Mindy's whereabouts. Rusty's wife, Rose, suspected he was the culprit and confronted him. A struggle ensued, and Rose hit her head on a rock and died, when. Will was at wits end. Sonni then found Marah with Anita Ybarra and convinced Reva, Rusty and Josh that she was not the kidnapper. When Rose's body was found, an anguished Rusty was certain that Will had iced her, but the D.A.'s office dismissed the evidence as circumstantial and let Will off. Determined to nab him, Rusty turned in his badge and became a private eye.

In July 1989, when Billy and Mindy returned to Springfield, Rusty was able to convince Mindy to help him get the goods on Will. Panicked by Rusty's investigation, Will had Anita confess to Marah's kidnapping, and she was duly committed. In time, Will realized Mindy was gaslighting him and he drugged her and held her at gunpoint. Worried that he'd still be put in prison by Rusty, Will took Mindy to the Cliff Hotel. Will attempted to throw Mindy off of the balcony of their suite, just when Mindy came to and out of her drugged induced state. Fortunately Will accidentally told Sonni where he was going with Mindy and Sonni alerted Rusty and Josh. Rusty arrived at the scene with Josh and Sonni and shot at Will, who ended up falling from balcony to his death. Sonni with Josh's help, were able to pull a dangling Mindy up before she would have fallen herself.

Afterwards, Sonni got involved with Roger Thorpe. However she soon realized that being around a nefarious man like Roger was not good for her mental health and she broke off the relationship and accepted a job in San Francisco. After spending Thanksgiving at the Bauer home, Sonni left Springfield for good.