It's one of the biggest scandals in the history of Neighbours - and fans have been waiting for more than a decade to discover what exactly happened between Sarah Beaumont and Dr Karl Kennedy.
Sarah, played by UK model turned actress Nicola Charles, was the hospital receptionist who left Ramsay Street in tatters after word got out she'd had an affair with Karl (Perth's Alan Fletcher) in 1998.
While the romance provided a huge ratings boost for Australia's longest- running drama, viewers never knew just what went on between the pair and were left hanging when Charles exited the show in 1999.
"Fourteen years ago when Sarah left, it was extremely difficult and complicated but it wasn't investigated back then as much as it should be. At that time, storylines were only touched on and not delved into," Charles says over the phone from her Melbourne home.
But on Monday, viewers will finally begin to receive the full story when Charles appears in the first of about 15 episodes.
"The way they've written her back in is so good. It's grittier and more real, which is something they've wanted to do with the script these days," she says.
"I was just flabbergasted when I opened the pages and saw some of the things that were actually spoken about in the scenes - about whether Sarah and Karl slept together and really got down to the nitty-gritty."
After leaving Neighbours, Charles' career failed to take off and she eventually put acting on the backburner to support her then husband, Irish actor Jason Barry, on his quest to make it in the US.
Following their divorce in 2008, the couple spent years consumed by a drawn-out custody battle for their two children, Freya and Nova.
Charles, who is married to British DJ Mark Tabberner, with whom she has a son, Archie, is now based in Melbourne and saw a return to Neighbours as a chance to relaunch her acting career.
"I wasn't working in America. I ended up having a custody battle which is well documented and my agent in Melbourne was contacted by Inside Soap magazine in the UK to do a 'where are they now story'," she explains.
"After the interview and shoot, I got an email from (the journalist who wrote the story) and he had moved back to Australia to become the new script producer on Neighbours.
"He said,'Would you ever come back?' and I said 'God yeah' because I've always loved Sarah. I thought she was fantastic back then and I knew that I could really do something fantastic with her now because I'm obviously very different, as we all are 14 years down the track."
Now in its 28th year on television, Neighbours will welcome back a plethora of its most popular characters in 2013, including Charles, Carla Bonner as Steph Scully, and Scott McGregor as Det. Mark Brennan, who was believed to have been killed on duty.
On the show, Karl has expressed his intention to reignite his relationship with Susan (Jackie Woodburne) and sets the ball in motion just as Sarah arrives back in town from the UK to finalise a deal which will see Susan lose her job.
"Back then she escaped by moving to the UK with Peter Hannay (Nick Carrafa). They've had a couple of children who are young teenagers now and their marriage hasn't worked out and, for business reasons, Sarah is bought back to Erinsborough," Charles says.
"She didn't actually want to come back but, because of her prior knowledge of Erinsborough, the company she works for asks her to complete the deal which unfortunately involves the Erinsborough News, which is where Susan works.
"No matter how hard Sarah tries to skirt around her past and be professional in her dealings in Erinsborough, the time arrives when you realise you have to get closure and sort things out with people.
"Sarah decides to revisit everything and fireworks erupt from that."
"I was just flabbergasted when I opened the pages and saw some of the things that were actually spoken about in the scenes . . . " Nicola Charles