Sixteen-year-old Sharon Collins and her single, paraplegic mother Doris lived in Madison, Wisconsin. Sharon's best friend was Grace Turner. When Sharon told her high school boyfriend Frank Barritt that she was pregnant, he wanted nothing to do with her or his child. Sharon and her mother decided to give the baby up for adoption because they felt they were unable to raise a baby properly. The baby girl was adopted by Alice Johnson and named Cassidy. Sharon and her mother moved to Genoa City. Alice later abandoned Cassie to pursue a man and left the child in the care of her elderly mother Millie. Cassie loved Millie, but it was very difficult for a woman of her age to keep up with a young child, and Cassie had no friends but her dolls.
Sharon ended up marrying Nick Newman, son of wealthy industrialist Victor Newman. When it appeared that Sharon and Nick's newborn baby Noah was going to die, Grace, who was now living in Genoa City too, and Grace's boyfriend Tony Viscardi tracked down Sharon's first child Cassie to help Sharon ease the pain of her loss. They convinced Millie to allow them to return Cassie, now 5 years old, to Genoa City and be united with her natural mother. But Noah lived, so Grace decided to keep Cassie until the "time was right" to tell Sharon. Grace fell in love with the engaging child, and kept the child's true identity to herself for over a year. After Grace finally told Sharon who Cassie really was, Cassie went to live with Sharon, Nick, and Noah.
One night Nick was out partying with friends while Sharon stayed home ill. Grace was helping out by spending the night in the nursery, but actually plotting to steal Nick away from Sharon for herself. Nick came home drunk and made love to a willing Grace, thinking she was his wife. The next morning when he realized his error he panicked and swore Grace to secrecy. (Sharon still does not know about this.) Grace used their secret to get a job as Nick's assistant at Newman, and renewed her attempts to steal Nick from Sharon. Time and again, she would plot for them to be together alone in the office, often late at night, even once arranging for the air conditioning to "go out" so she could keep removing more and more of her clothes and seductively rub her skin with ice to seduce Nick. Tony broke up with Grace due to her obsession with Nick and was later killed when psycho Tricia Dennison backed her SUV over him on his motorcycle - it was never proven to be anything other than an accident.
Grace used their secret to get a job as Nick's assistant at Newman, and renewed her attempts to steal Nick from Sharon. Sharon was going with Nick on a business trip to Denver, but when Noah fell sick, Grace went with him instead. Nick was angry with Sharon and finally allowed Grace to seduce him there. Sharon showed up the next morning to surprise him, but was stunned and to overhear outside the hotel room door Grace telling Nick that their lovemaking was incredible. Sharon took the kids and moved out, and refused to forgive him for his infidelity. They eventually reunited and were so happy together that Nick wanted to adopt Cassie legally. But Alice had finally returned to Millie's, expecting to find Cassie. Christine Williams represented the Newmans and Michael Baldwin represented Alice. Grace Turner got involved with Michael about this time, running into him several times at a bar, where they discussed her hatred of the Newmans and would banter and flirt. At one such meeting Michael surprised Grace by presenting her with a picture he sketched of her, and enlisted her help in finding out if Alice would really rather be paid off than get custody of Cassie. Grace realized they had a mutual evil streak, and gave him a quarter as retainer to become her lawyer. During one of their meetings about the case Grace kissed Michael as a reward for his efforts, and they ended up having sex on Michael's desk. But Grace felt betrayed when Michael won the custody case for Alice despite her efforts. When Victor found out that Grace had come between his son and his wife, he arranged for a job for her at a Newman subsidiary in New York City.
Over the years since, whenever Nick and Sharon's marriage was on the rocks, Nick would give Grace a call or invite her to come to Genoa City to ease his sexual desires and get back at Sharon for not being the perfect wife, as he did after the miscarriage of their baby. Sharon's affair with Diego Guittierez was her reaction to this visit. Sharon later admitted the dalliance to Nick. Nick took it very badly, beat up Diego, then called up Grace and let her sooth his bruised ego in bed.
In late 2003 Sharon was shocked realize software entrepreneur, Cameron Kirsten, had arrived in town to make a deal with Newman, and Nick was handling it. It was revealed that while she was gone all those months, she met up with Kirsten in a bar in Denver, they went up to her hotel room, and Sharon ended up having sex with him and being beaten to a pulp. Sharon had been afraid to risk her marriage by reporting it to the police, so she stayed away long enough for her bruises to heal. Cameron began taunting and threatening Sharon that he would tell Nick about "their affair" until New Years eve, when he told her to meet her at a fleabag hotel for another round or else. Sharon met him there, but refused to go through with it. When Cameron attempted to rape her, Sharon clobbered him over the head with a champagne bottle. In a panic, she dragged the body down the back stairs and hid it behind a dumpster, and before long it was buried in snow.
Cameron was declared missing, and Grace Turner arrived in Genoa City looking for him. It seems they were involved in a long-distance romance, and Grace was fraught with worry over his disappearance. Sharon had confided the events of New Years Eve to Attorney Michael Baldwin who kept advising her to go to the police. Instead, knowing the desk clerk could identify her, and because it was beginning to thaw, she moved the body. Sharon made a wrong turn, ended up at a dead end between buildings in a seedy part of town, and was surrounded by thugs who wanted to rape her. She talked them into opening the trunk for a blanket, but they got scared and fled when they saw the dead body inside. Sharon drove off into the night and ended up at a biker bar out by the lake. On the way out after using the restroom, Sharon ran into Grace who hassled her about her appearance and her panicked state. Sharon finally had enough, and took her to the back of the car to show her why she was panicking, but the trunk was empty. Sharon made it home, but was still jumpy for days. Grace dropped by often, accusing her of killing her boyfriend. Sharon began to be haunted by the rotting body of Cameron. Then old friend Larry Warton paid her a visit bruised and beaten, just released from the hospital, asked Sharon about the body. Sharon, relieved that she wasn't imagining what happened, and gratefully, confessed the whole story. It seemed he had seen her arrive at the bar that night, popped the trunk and taken the body and hid it for her. Sharon was relieved when Larry promised to keep mum. But the haunting kept on, and the police started asking questions.
Sharon thought she was going crazy and insisted Larry show her the dead body. Larry took Sharon, accompanied by mother-in-law Nikki, whom Sharon had confided in, down into the wet, stinking, rat-infested sewer, and found the body. Although she could identify the clothes as Cameron's, the face was too decomposed to recognize. Sharon continued to be haunted by Cameron and taunted by Grace until the body was discovered. Much to everyone's shock, the body turned out to be that of Cassie's father Frank Barritt who had stopped trying to see Cassie around New Years, so Sharon became the number one suspect. At her last haunting prior to her arrest, Cameron finally said, "Gotcha." to her, and sent her running screaming from the house. Later on after Cameron showed up at the Athletic Club, very much alive, Larry, Sharon, Michael Baldwin and Nick figured out that Grace was helping Cameron with his plot for revenge on Sharon and convinced her to help them expose him. The body was found eventually after it washed out of the sewer, and turned out to be Sharon's ex-boyfriend and daughter Cassie's father Frank. Cameron had set Sharon up for Frank's murder. Luckily for Larry, when all was said and done, he was not implicated. But Cameron escaped in his private jet with Sharon held hostage. Nick stowed away in the plane and jumped Cameron. They managed to get him into a parachute, and all three bailed out of the plane. Cameron landed in a tree which broke his leg, but Nick and Sharon made him walk to civilization where they called the police and turned him over. Presumably Grace got off for helping Sharon, and returned to New York City.
Ten years later, Grace received a call from Nick that he needed her help and was sending the Newman jet for her. Later, Nick arrived at Grace's room at the GCAC to find her wearing only a teddy. Nick set her straight, that it was not a booty call, he just needed some information that only she might know. Grace mentioned that Cassie's death had been such a tragedy, and that she had never gotten to give her condolences. Nick shocked Grace with photos of Mariah who looked just like Cassie, and asked Grace to tell him about the day Cassie was born. Grace recalled that Cassie had been born in a hospital, and there had been a nurse named Helen who had kept Doris and Grace out of the delivery room so that no one had ever seen the baby. Nick thanked Grace for the information, and Grace returned to New York City. Nick followed up with Sharon's former doctor in Madison, and discovered that Sharon had had twins, the second one being Mariah, who had been sold to cover the doctor's gambling debts.
Five months later, Grace showed up at Sharon's door, supposedly passing through and stopping to congratulate her on her remarriage to Nick. Grace was surprised to meet Mariah and her resemblance to Cassie. Sharon reluctantly admitted that the wedding did not happen, that Nick had caught her in an unforgivable lie and moved out. No love lost between them, Sharon pretty much threw Grace out, sure that she would go running to seduce Nick. Grace came onto Nick at The Underground, and Nick revealed that Sharon had changed the paternity test results, robbing him of his daughter Summer. Pouring drinks for them, Nick told Grace that he was done with Sharon this time. Grace kissed him, they tore off each other's clothes, and made out in a booth. But Nick stopped, and told her to leave, that he was finally breaking the pattern, and needed to go away to think about what to do with his life.