She first appeared as a central character in 2004 and went on to serve as the main antagonist in 2005 before becoming one of the two secondary antagonists in 2006.
From the moment she stepped off the helicopter all fur coat, bling shades and dazzling diamonds, it was clear that Sadie King meant business. The bitchy blonde, who married wealthy Tom King’s eldest son Jimmy, took an instant dislike to her father-in-law’s fiancée Charity Tate and made her feelings very clear. She was best friends with her sister-in-law, Colleen, then married to Carl. She wasn't happy when he began dating Chas Dingle.
While her hatred of Charity was intense, Sadie was also rapidly going off her husband. Jimmy was a simple man who wanted a big family and his pretty wife by his side. Sadie, however, had other ideas and had contraceptive injections behind his back. When he forced the issue, Sadie came clean but her deception jeopardized their marriage, with a devastated Jimmy furiously demanding a divorce.
Sick of being rejected by Jimmy, Sadie began an affair with local mechanic Robert Sugden – who couldn’t believe his luck. Her love life might have been complicated, but Sadie’s big interest was money. Knowing that Jimmy’s rejection meant her position in the King family was threatened, Sadie began to hatch a plan to ensure Charity never became Tom’s wife. Employing a private detective to trail Charity, Sadie bribed her ex-lover Cain Dingle to get Charity in a compromising position.
With Tom already unable to contain his jealousy over Charity, Sadie put in the final dose of poison by giving him the incriminating photos on his wedding day. She’d successfully sabotaged the wedding, but Sadie’s actions were going to cost her dearly. Charity decided to wage war against her nemesis by sleeping with Jimmy and videotaping the whole event! In the film, Jimmy revealed everything about Sadie’s plots, her alliance with Cain and the state of their marriage. A triumphant Charity burst into Jimmy's birthday party and told everyone present that they'd been having an affair, much to the fury of Sadie and the King family. Charity played the tape after she was accused of trying to cause trouble between Sadie and Jimmy.
The repercussions saw Tom disown Jimmy and Sadie, their marriage ended and Sadie found herself alone. She had no intention of losing everything - while she knew her marriage was beyond saving, Sadie launched a bid to get back into the family business. Enlisting Cain Dingle’s help again, Sadie purchased land the Kings wanted for their development and blackmailed her way back into the company. She may have got what she wanted in terms of money, but she wasn’t welcomed back into the fold by Tom.
Lonely, isolated and desperate - she slept with Cain – much to his delight. When she rejected his advances later, Cain took a terrible revenge by killing her beloved dog, Damon. However, while Sadie was devastated by Damon’s murder, she had no intention of resting on her laurels. When her ex brother-in-law Max King died, she used Tom's vulnerability to her advantage and was back in the fold after blackmailing Zoe Tate to sell Home Farm to Tom, who was so grateful he even made a move on her. But, although it would have been the answer to all her problems, Sadie couldn’t bring herself to get it on with Tom, unsurprisingly.
It transpired that Matthew had been in love with Sadie for years and they were even sleeping together before she married Jimmy. Now they were both free, the couple started sleeping together again and Matthew, for the first time, let his guard down. Things were looking perfect for the pair as Tom prepared to step down as head of the company and hand it over to Matthew. But just before he signed on the dotted line, Jimmy exposed the couple’s affair and Tom went mad. He gave Matthew a choice – be with Sadie or take over the company. Matthew chose the business, leaving Sadie devastated. She retreated to lick her wounds, but Sadie was back with a vengeance just weeks later.
Having snared a rich fiancé in the form of dimwitted Alasdair Sinclair, she was a marriage ceremony away from being filthy rich again. But there were two problems standing in her way, Alasdair’s suspicious mother Rosemary and ex-lover Matthew. Even though Sadie managed to get him down the aisle, it was the briefest marriage ever. Stopping her outside the church, Matthew confessed his undying love for Sadie and gave up King & Sons. Tom threw him out of the family and the couple were on their own. Sadie had no intention of being left with nothing and was soon coming up with ways to get Matthew back in business. Upon hearing that haulage rival Don Clough was selling his business, Sadie encouraged Matthew to buy it and dupe his brothers into believing false information that jeopardized their own bid. It worked, but it ensured that Matthew completely burned his bridges with his brothers – with Carl disowning him too. Sadie was hell bent on ensuring that her man and her business do brilliantly – at the expense of anyone who gets in their way.
After Matthew discovered that Sadie was involved in the Show Home Collapse (she paid Cain to vandalize it) which left his brother seriously injured, he ended their relationship and was welcomed back into the family. After the breakup, Sadie became hell bent on getting even with the King family. Along with Cain, they devised a plan to kidnap Tom. In the end, Cain left with £2,000,000 and Sadie with nothing except a Sports Car BMW.
The last reference to Sadie was when she sent flowers to the funeral of Tom. However, the flowers were discarded by Matthew.