On the morning of the wedding, Rosemary tried to bribe Sadie not to marry her son but Sadie refused, threatening to get Alasdair to put her in an old people's home if she didn't back off. She married Alasdair but left the church with her ex, Matthew King. Rosemary wanted Sadie and Alasdair's marriage annulled so they wouldn't have to give her a settlement. However, Sadie tricked Rosemary into thinking the marriage had been consummated so they agreed that in exchange for the Sinclair business most valued by Rosemary, Sadie would get the marriage annulled. Rosemary got revenge: once the papers were signed, she revealed that the business was worthless and claimed that the meal served prior to the signings was Sadie's horse, Cossack, (this was a lie, but Sadie believed it).
A shared hatred of scheming Sadie meant she soon bonded with wealthy businessman Tom King. Rosemary quickly realised that getting involved with him would be advantageous to both of them and began putting business his way. Tom and Rosemary's relationship was soon more than just business. A spark developed between them and they became lovers – to the horror of Tom's sons, who didn't trust Rosemary. They were right to question her motives.
While she had a fancy house and plummy accent, Rosemary's fortunes were fading fast. The family home, Oakwell Hall, belonged to her nephew and her money was almost gone – thanks to her sons. Grayson, in particular, had almost drunk the well dry as his gambling and extravagant living meant Rosemary was constantly bailing him out. Sick of it, she cut him off – prompting more tension in an already fraught relationship between her and Perdy.
Surprisingly, Rosemary had another ally at Home Farm, Chas Dingle. She could see that he and Rosemary were happy together and once Rosemary's motives were exposed, she convinced Carl and his brothers to leave her alone. Unfortunately Chas's sympathy evaporated when Rosemary and Tom started interfering in her and Carl's relationship. Tom didn't think she was good enough for Carl and when Rosemary told him she agreed, he bullied/blackmailed Chas into ending things with Carl and move out of Home Farm. They reconciled briefly after Tom's death but Carl soon ended things again and Rosemary was surprisingly sympathetic when she saw how upset Chas was.
Meanwhile, Rosemary had moved into Home Farm. As her relationship with Tom was progressing, she felt more secure, but clashed repeatedly with Chas Dingle and Tom's secretary, Edna Birch. With everyone opposed to his and Rosemary's relationship, Tom decided to prove he was serious about her and shocked her by proposing. She accepted and they married in a romantic Christmas Day ceremony. The ceremony took place at the village church and the reception was held at Home Farm. Tom announced he was giving Rosemary Home Farm Estate as a wedding present, much to the disgust of Tom's sons. Rosemary was shocked when Tom told her that he wanted her to leave it to Carl in her will, rather than Grayson. This could have been her motive for murdering Tom when he died later that night, leaving her a widow. She was one of ten people suspected of the murder.
Feeling lonely after Tom's death, things didn't improve. She continued to live at Home Farm as she was entitled to do, as Tom's widow. Jimmy and Matthew thought she had murdered Tom and wanted her out. She was already friends with Charles Vaughan and he was a little too keen to comfort her. A lot of people were suspicious, including Matthew King. He reported Charles's constant visits to the DCI in charge of the investigation, giving her no choice but to pass it on to her bosses.
Relations went downhill further when Rosemary found out her stepsons planned Tom's funeral for when she was away, so she took the body. The Kings blanked her at the funeral and were angry to discover, during the reading of the will, that Tom left Home Farm to them providing they gave Rosemary a home for as long as she wanted. They were shocked again to find they had a sister, Scarlett Nicholls. Carrie, her mother, met Tom when she was nursing their mother, Mary King, before she died. The Kings were angry, feeling Tom had betrayed their mother. Carl, in particular, took it badly as they had had a brief fling. Rosemary used it to her advantage, becoming allies with Carrie.
Perdy told Matthew that Rosemary had been widowed mysteriously before. Ray Sinclair, her first husband, died in a shooting accident and Matthew convinced Perdy to tell the police, claiming it was vital evidence. The police questioned Rosemary who knew Perdy told them but was shocked when Matthew told her he had found out from another source. Needing to talk to someone, Rosemary told Zak Dingle that Ray had killed himself because she made his life hell.
The police came arrived a few days later and arrested the Kings for conspiracy to murder. Rosemary wanted them out of her way - if they went down for murder, that was even better. She continued scheming by telling Andy Sugden to evict Katie and Perdy from Butler's Farm. She called him in, telling him under his tenancy agreement, he could not sublet any part of the farm if he wanted to continue renting it. Andy told Katie and Perdy that they would have to find new premises and Rosemary told them they could use the stables at Home Farm in exchange for a 10% stake in the business. Perdy was furious at Rosemary muscling in but Katie was thrilled, seeing it as a chance to move up in the world.
When Scarlett found out she had 3 brothers, Rosemary delighted in their fury about her hanging around. She was soon distracted by family problems of her own when Perdy miscarried again and needed an emergency hysterectomy. Rosemary knew Grayson was lying and forced him to tell her the truth. Distraught about not having grandchildren, she felt the marriage wouldn't last and wanted Grayson to leave Perdy but he won't.
Rosemary also became good friends with Zak Dingle. She also became close to Belle Dingle after Rosemary agreed to pay the fees for her to go to private school. Zak worked as gamekeeper at Home Farm and they became good friends. Lisa Dingle suspected they were having an affair. This wasn't helped by Shadrach, Zak's brother, making comments about Rosemary. Lisa flew off the handle, slapping Rosemary and threw Zak out but Rosemary talked her round.
Shortly afterwards, Grayson borrowed money from Rosemary. He used it for a bet on Hari Prasad's horse but it lost and Grayson told Hari to get the money back. Rosemary soon got involved, telling Hari not to worry about the money he owed her. She also gave him the money he needed to repay what he'd taken from the vet's surgery accounts to buy the horse if he told the police he overheard the Kings talking about the murder weapon. Hari agreed and got Louise Appleton to back him up.
Matthew knew Rosemary was behind Hari and Louise's statements and didn't think much of them. Hari was in trouble when Louise found out he was lying and went to the police. He ran her car off the road, trying to stop her. On the day of the trial, Hari and Louise didn't appear as Louise told the police that she and Hari had not heard the King brothers discussing Tom's murder. She also told them how her accident happened and Hari was arrested for attempted murder and attempting to pervert the course of justice.
Rosemary was determined to get her revenge on the Kings and see Grayson married to a woman who was not "a danger to the family name". Trying to get Perdy out of the way, she meddled with Perdy's pills so Perdy thought she was going mad. She wanted Grayson to find someone better and refurnished the attic as a nursery, drugged Perdy, and damaged her car. Rosemary completed her goal by confessing after Perdy found the nursery. Unfortunately the damage was done, Perdy went for Rosemary. Grayson persuaded her to come out and pretending to believe her, led her into a waiting ambulance. She was taken to hospital and sectioned.
On 13th September 2007, Grayson went to see the family doctor and he told Grayson about the pills he had prescribed for Rosemary. Grayson learned Perdy's symptoms were the result of mixing the two sets of pills prescribed. He confronted Rosemary, who admitted what she had done, so Grayson kicked her out. He told her not to return. She stayed initially at the B and B, and then Paddy's. The next day, she saw Perdy in the Woolpack, who told the whole pub that Rosemary had poisoned her. Zak took Rosemary home and she told him that Perdy had told the truth. A horrified Zak told Rosemary to stay away from him and his family and left. She bumped into Grayson in the village, who told her to leave. She refused and Grayson told her there was nothing left for her in Emmerdale. She then vanished without a trace.
On 31st October, Edna was looking for her dog Tootsie. She found her but didn't notice what she was sitting near - Rosemary's bag and passport. A few weeks later Paddy Kirk, and Marlon Dingle were walking down a country road when they spotted Rosemary's handbag and passport lying in the grass. They called the police, who searched the bag and found a diary, and on 13th September (the date she was last seen) it said MK MF in her handwriting. The police suspected this meant Matthew King, Manor Farm, meaning Rosemary had met Matthew at Manor Farm (the Kings' property) that day. They told Grayson and found Rosemary's car abandoned at Manor Farm, and two empty coffee cups on the table, one with Matthew's fingerprints and the other with Rosemary's fingerprints. They found traces of her blood on the floor and concluded Matthew had invited Rosemary to Manor Farm, made her a coffee and then murdered her. Matthew was arrested, charged and held on remand in prison. The whole village turned against him, believing he was a murderer. However, Grayson hired a private detective to find her and the detective told Grayson that Rosemary was living in Miami. The detective brought Grayson a letter from Rosemary in which she told the truth, that she faked her death and framed Matthew for her murder. Grayson went to Home Farm to tell Matthew but saw him and Perdy kissing and discussing their affair. Grayson kept the letter and Matthew was imprisoned.
On Christmas Day, Perdy found the letter and confronted Grayson. She told him she was going to the police but she and Grayson had a fight. During which, he grabbed the letter and did a runner but Carl and Jimmy caught him. They took the letter to the police claiming he had been so busy that he hadn't realised what it was. They believed him and he wasn't charged.
"Only me!" (First line)
"To make myself perfectly clear I'll use your vernacular. I'll have you, I'll hang you on the dry, I'll finish you." (to Matthew King, threatening him to stop interfering in Rosemary and Tom King's relationship)
"I'll never give up on you Grayson." (Last line)