Fair City star Amilia Stewart said seeing her screen kidnapper again was like "seeing a ghost" when he returns to Carrigstown.
Amilia, who plays Katy, returns to the RTE soap as well as Johnny Ward as abductor Ciaran, for its 30th anniversary.
There is an hour-long special tonight and some dramatic scenes to come over the next few weeks.
The actress said she could not be happier to be working with her childhood chum once again - a far cry from their screen characters.
The pair grew up together in Walkinstown and she said Johnny was someone who "always looked out for me".
Amilia told the Herald that when she got an email from the soap's producers asking her if she would go back she was entering her second year of the stage play The Snapper.
"I also had my wedding coming up so had to check the dates worked around that too.
"I immediately rang Johnny and was like, 'Did you get this email too? Are you going to go back?'
"To be honest, it would be a bit weird bringing one of us back without the other. I just remember thinking I really wasn't expecting to get the chance to go back," she said.
Ciaran has not been seen in Carrigstown since being stabbed and falling from a pier over two years ago at the culmination of the dramatic "Katy in a box" storyline.
Amilia's character has been living in Aberdeen with Debbie while she undergoes therapy and works on rebuilding her life - and even writing a book about her abduction.
But her dad's 50th birthday and her grandmother developing dementia bring her back to Carrigstown - with painful memories and the bombshell of encountering Ciaran.
"It's going to be a big shock when she sees him again," said Amelia.
"It's like seeing a ghost. She can't believe he's still alive when everyone thought he was dead.
"It's really scary for her. Their relationship did become very unhealthy. There was definitely some Stockholm Syndrome there.
"It was just the two of them for so long and she came to count on him more and more towards the end."
Viewers will see them trying to work through the intricacies of their relationship in the coming weeks, with some dramatic twists in store.
Off-screen, the actress could not be happier as she gears up to tie the knot with fiance Conall Keating.
They will have a spiritualist ceremony at a hotel in Sligo.
Amilia said her time as a theatre producer meant she was able to keep a cool head when planning major events.