IT'S a mystery that has haunted Irish society for 20 years. But the decision by gardaí to officially upgrade the disappearance of Deirdre Jacob to a murder investigation is a major development that offers the possibility of closure.
Deirdre was last seen walking alone on a country road towards her home, about 1.5km outside Newbridge, at 3pm on the afternoon of July 28, 1998.
Within the next half hour the 18-year-old primary school teacher student vanished without trace, as if she had been swallowed up by the elements.
Deirdre's was the last name added to a group known as Ireland's Missing Women, who number seven in total.
All vanished in the Leinster area between 1993 and 1998, sparking fears they may have fallen foul of a serial killer.
However, gardaí definite suspects and motives in three of the cases: Fiona Pender who vanished in 1996, Ciara Breen in 1997 and Fiona Sinnott in 1998, and are satisfied they are unconnected.
With regard to the disappearance of American student Annie McCarrick in 1993, it has been reported that a cold case review identified the suspect as a senior member of the Provisional IRA in Dublin.
The disappearance of Eva Brennan (40) four months after Ms McCarrick is perplexingly the only case that has not received the same level of Garda scrutiny or, indeed, featured in public appeals.
The cases of Jo Jo Dullard, who was last seen on November 9, 1995, and Deirdre Jacob remain open.
These disappearances have been the subject of one of the longest-running active investigations in recent history, including a number of cold case reviews by specialised officers.
However it has never been established what happened and whether the two remaining cases are connected to the same killer.
For Deirdre Jacob's parents Michael and Bernie yesterday's announcement has, hopefully, brought closure a little nearer.
Despite its initial classification as a missing person case, gardaí always pursued their investigations in the belief Deirdre was abducted and murdered. Jo Jo Dullard is believed to have suffered a similar fate.
The decision to upgrade the Jacob investigation, as revealed by Chief Supt Brian Sutton, is based on new information the gardaí received following a cold case review conducted over the past year. Gardaí do not make such public disclosures without having strong grounds on which to do so.
Sutton said officers are following a number of new leads and progress is being made. It is the first serious indication Deirdre's disappearance will be solved and the prime suspect will finally be brought to justice.
Upgrading the investigation to a murder probe is the first indication that Deirdre's disappearance will be solved.
The development has refocused the spotlight on Ireland's most feared sexual predator, Larry Murphy aka the 'Beast of Baltinglass'.
Murphy, who has been officially elevated to prime suspect, has been a person of interest in the Jacob investigation for 18 years - and with good reason.
The family man from Co Wicklow first came to attention after the horrific abduction, multiple rape and attempted murder of a young woman he randomly spotted on a street in Carlow town.
At the time Murphy, a carpenter, was working on renovating a house there. His behaviour and methodology displayed all the hallmarks of a serial killer. Shortly after 8pm on February 11, 2000, Murphy pounced on his victim as she walked to her car.
Murphy punched the woman, fracturing her nose, before bundling her into her car and driving to his own vehicle parked out of sight. He forced his victim to strip, tied her hands with her bra and shoved her into his car. He drove 16km north of Carlow town where he gagged and raped his victim.
He then forced her into the boot and drove to the Glen of Imaal, stopping on an isolated track he knew from his hobby as a hunter.
Here Murphy raped his victim twice more and attempted to suffocate her.
Murphy's victim began a frantic effort to escape. As she tried to get out of the car, he slammed the door on her legs.
But fate intervened when local men Ken Jones and Trevor Moody, who were out hunting, saw the commotion and went to investigate.
Murphy sped off, leaving his victim behind.
Fortunately the men recognised Murphy and went to the gardaí. The following day he was arrested.
Murphy never offered any explanation and pleaded guilty. He was a model prisoner but never participated in any rehabilitative programmes.
Experts say Murphy's behaviour had all the traits of a serial killer. He stalked his victim before making his move when she was most vulnerable.
He also brought her to the wilderness of the Glen of Imaal, an area he was intimately acquainted with, where the chances of being discovered were practically non-existent.
This is what criminal profilers refer to as a "killing field": a location where the killer feels secure.
When Murphy finished his sentence in 2010, he immediately left the country and began moving between cities in Holland, France and Spain.
Gardaí notified their colleagues in Europol, who in turn issued a Euro-wide police alert.