The father of Deirdre Jacob, who has been missing since July 1998, has appealed to her killer to tell them where she can be found.
Friday marks the 25th anniversary of her disappearance and murder.
An Garda Síochána has said there continues to be "an open and active investigation" into her disappearance by a dedicated investigation team based at Kildare Garda station.
Deirdre was a trainee teacher from Newbridge, and had returned home from London for the summer.
The then 18-year-old went missing shortly after 3pm on the afternoon of July 28th, 1998 after she had been visiting her grandmother a short distance from her home.
The last sighting of Deirdre was as she reached the gateway to her family home after a 25 minute walk from Newbridge town.
In August 2018, detectives on the case upgraded it to a murder investigation.
Her father Michael Jacob told Newstalk Breakfast he believes someone has information that can help.
"We believe that there is a person or persons that has information that would be vital in the investigation," he said.
"She had walked from Newbridge, about 25 minutes walk, and she had just crossed the road into our gateway when a motorist driving past - towards Newbridge - spotted her.
"They recognised her by the fact that she was carrying the large CAT bag".
An example of the distinctive CAT bag Deirdre Jacob had when she disappearedMr Jacob said there were no further sightings of her after that point.
"We know nothing at all, it seems as if she just vanished, there was never any leads or any sightings or anything that made any difference after that," he said.
"There were many sightings of her as she walked from Newbridge to our gateway, but not after that".
'Was she being watched?'
Mr Jacob said there is not a day he and his family don't think about what happened.
"The initial shock when we found that Deirdre wasn't in the house and wasn't with any of her friends - that was a very, very severe shock," he said.
"I suppose at that time we didn't realise this shock because we were searching with such vigour to try and find her.
"Then as time moved on the shock became great, became very severe, and that has continued on day after day.
"There's no day that we don't ponder as to what may have happened and even in our minds try to retrace the steps that Deirdre made from Newbridge.
"As to what might have happened: was she being watched, was someone trailing her or what? We just don't know but you try to figure out that in your mind".
'25 years is a long time'
Mr Jacob has a message for the person who killed his daughter.
"We would plead with them to give that piece of information and indicate where Deirdre's to be found, so that we could have her back," he said.
"That would mean a lot to myself and the family.
"It would never answer all the questions, but nevertheless we appeal to that person to consider the length of time that we have suffered - 25 years is a long time," he added.
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