Why gardaí must never give up searching for Ireland's disappeared
The disappearance without trace of seven women in Ireland during the 1990s sparked fears that they may have been the victims of a serial killer.
Along with Ciara Breen (17) and Fiona Sinnott (19), the names of Annie McCarrick (26), Eva Brennan (40), Jo Jo Dollard (21), Fiona Pender (25) and Deirdre Jacob (18) remain among the most high profile - and chilling - unsolved missing persons cases in Irish criminal history.
Despite several exhaustive, highly specialised garda investigations spanning three decades, the only conclusion that connects all the cases is the belief that the missing women were murdered and their bodies buried in unmarked graves.
There is probably no greater distress for a family than when a loved one suddenly vanishes as if into thin air leaving no clues, no sightings and no explanation.
Their families have been left to endure unimaginable anguish, their lives suspended in time, as they desperately cling to the hope that somehow their loved ones will reappear.
In some of the cases, parents have gone to early graves still haunted by the disappearance of a cherished child.
For those left behind, there is only the hope that somehow gardaí will help bring closure with the recovery of remains for a Christian burial - and the unmasking of the monster responsible.
The horrific murder of Elaine O'Hara at the hands of Graham Dwyer brought back memories of the missing women and invoked darkest fears of the fates they may have suffered.
It would be incorrect to think that the gardaí have not made progress in these investigations over the years.
Definite suspects have been identified for the disappearances of Ciara Breen, Fiona Pender and Fiona Sinnott.
In all three cases, gardaí and the families are satisfied that the missing women knew their killers and that the motive for the disappearances were rooted in those relationships.
But, in the absence of remains, it would be impossible to sustain a charge of murder against the suspects.
Last December, gardaí also conducted an extensive forensic search in woodlands outside Portlaoise for the remains of Fiona Pender, who was pregnant when she vanished in August 1996.
Despite being unsuccessful on this occasion, there is a determination that a grave will be located because detectives have received good-quality information from someone close to the man believed responsible for Fiona's death.
The same is also the case with Fiona Sinnott, who went missing in Wexford in February 1998.
The prime suspect, who has continued to live in a small, rural village in the county, is understood to be "rattled" by recent developments in the case, according to local sources.
The first of the women to vanish without trace was American student Annie McCarrick, who was last seen alive in Johnny Fox's pub in the Dublin Mountains in March 1993.
However, according to retired Cold Case Unit detective Alan Bailey, a suspect has been identified in recent years.
It is understood that the killer was a senior member of the Provisional IRA who covered up his crime with the help of his Republican comrades.
Sources have revealed that the Provo and his henchmen moved the body at one stage before the organisation helped him to leave the country.
However, no concrete suspect has ever been identified for the disappearances of Eva Brennan, Jo Jo Dollard and Deirdre Jacob.
Eva Brennan vanished in Terenure in Dublin in July 1993, four months after Annie McCarrick went missing.
Jo Jo Dollard (21) was last known to be alive when she made a call from a public phone box in Moone, Co Kildare, and appeared to be about to take a lift with someone.
Deirdre Jacob was 18 when she vanished while walking towards her home at Roseberry, Newbridge, Co Kildare.
No suspect was ever identified in these three cases, although there has been intense speculation that notorious sex attacker Larry Murphy may have been involved in one or maybe more incidents.
Deirdre's family have said publicly that in the absence of evidence, they believe nominating Murphy as the suspect in her disappearance may have unduly influenced the minds of potential witnesses.
The new developments in the cases of Ciara and Fiona will be closely followed by all the other families.
No doubt they will hope that the relatives of the two girls get them back - even if after all these years it proves impossible to bring charges against their killers.