Please help us find out what happened to our missing sons

Ever since, they have been searching for answers, their broken hearts resigned to the fact that their boys will never come home.

Today, they lead shattered lives grasping at the hope that somebody's conscience will crack and the bodies of their children will be given back so they can be buried with dignity.

This week, through the Irish Independent, they appealed to anyone who has information on the disappearances to come forward.

Professional women from middle-class Limerick, they were devoted parents who shared a bond with their sons that was the envy of other mothers. Aengus and Desmond were the light of their lives, the family dotes who always remembered birthdays and never gave their parents a sleepless night.

When they disappeared in the winter of 1999/2000, their comfortable, happy lives were turned upside down. Nancy Shanahan, a schoolteacher, and Julia Walsh, a hospital supervisor, didn't know each other before their sons went missing but they soon realised there were shocking similarities between their cases.

Aengus and Desmond were just 20 and 24 when they failed to come home.

They vanished within just five months of each other. Their final sightings were at locations just minutes apart in the heart of Limerick city's Georgian quarter.

Another critical link is that they both worked at Dell: Aengus on the assembly line, Desmond in security. Gussie and Des, as they were often known, were honest and hard-working employees whose diligence in the office was also reflected in the way they treated their parents.

They came home when they said they would. They were always at the other end of their phone. But in the final weeks of their lives, some say the happy-go-lucky men, who looked much younger than their years, were frightened and anxious.

Close friends, too fearful to be identified publicly, say they had fallen in with a "a dangerous crowd".

The ringleaders were older men who set out to exploit the youngsters' weakest flaw – their trusting natures and naivety.

New information that backs up these claims has now come to light due to the courageous and painstaking work of a former police officer.

Limerick local Catherine Costelloe spent her career with the London Metropolitan Police. When she finished service, she came home and became actively involved in helping families of missing people.

As a policewoman on the streets of the British capital, she worked on countless investigations and played a vital role in cracking one of the biggest paedophile rings operating in the city.

But for her, the case of the missing Dell men is one of the most sinister she has ever taken on.

Today she spends much of her time trying to unravel the truth and find their bodies.

For the last three years, she has interviewed dozens of people close to the pair and others who saw them in their final days and hours. She has carried out door-to-door enquiries, distributed leaflets and posters, and obtained critical evidence about the case.

It includes compelling CCTV footage of Aengus outside Coopers pub on St Joseph Street on the Friday night of his disappearance, just minutes before he was last seen alive. It was February 11, 2000.

Catherine sent the footage for analysis to one of Britain's most experienced forensic firms, who have confirmed that unusual activity in it suggests it holds potentially critical value. In an exclusive interview with the Irish Independent, she said: "Everything points to murder. There is no doubt in my mind about that. Aengus and Desmond were incredibly well-liked but in the final weeks of their lives they were clearly innocent in their choice of company.

"The links between their disappearances are so astonishing that we cannot rule out the possibility they are buried together.

"Strangers have called us out of the blue saying the men were killed, and giving us locations to search, the most recent being that Aengus was thrown over the wall of an ancient graveyard near a railway track. That area has still to be searched like many others we have our suspicions about."

A retired bank manager, Aengus's father Bob Shanahan recalls the last day he saw his son. He had dropped into the bank to return a small sum of money he had borrowed from him. It was the day before he vanished.

"He was so reliable like that. That day, I remember him looking around at all the people in the bank and saying to me, 'Dad, imagine if they knew I had come in here to pay you back £40'. I joked 'they might ask me how much interest I was charging you'! We laughed about it and he was gone. He just disappeared out of the blue."

But Nancy's final memories of her son are more disturbing.

"Shortly before he vanished, he came to me one day and we had a cuddle. Aengus was always in good humour, but this day, I felt he was afraid. He told me he was cold. I see that now as a sign of fear. Something was worrying him."

Julia Walsh is also concerned that her son was in danger in the weeks before he vanished in September 1999.

Everything had been going well for him at the time. A keen musician who was meticulously organised, he was in a gay relationship, and had been offered a promotion in the week before he died.

At the time, Julia was nursing her husband, Thomas, who had terminal leukaemia and died two years after his son's disappearance, never giving up hope that one day he would be found.

Before Desmond went missing, he was sporting injuries. He had suffered bruising to his ribs and had difficulty breathing. A work colleague said he had come into work one day "black and blue".

On the night he vanished, he was seen in a preoccupied state close to Costello's pub, a short distance from where Aengus went missing.

What is also unusual is that his phone continued to ring for at least three days after he disappeared, but nobody answered.

Julia says: "There are so many unanswered questions about his disappearance but one thing I am sure of is that he was killed.

"Time doesn't heal in a situation like this because you can never grieve when you do not have a body and you do not know the truth about what happened to your child."

Julia and Nancy's fears are echoed by one of the world's foremost experts on suicide, Professor Ella Arensman, director of research at the National Suicide Research Foundation.

She became interested in the cases after meeting Nancy and Bob Shanahan and taking a close look at the missing men's lives.

"I believe we are talking about murder," she says. "I would like to know if there has been a systematic investigation of the links between Aengus and Desmond, and the events that could have contributed to the disappearance of these two men in such a short space of time. We need a investigation into all of the links between them."

Costelloe is adamant that the cases can still be solved.

"Some witnesses are terrified but if we stand together, the terror will stop. The connections between these cases are too alarming to be ignored.

"Young men should never vanish without trace. That should not be allowed to happen in any democracy. Every single avenue must be explored. After all, Aengus and Desmond could be any of our sons."

If you know anyone with information about the disappearance of Aengus or Desmond, please call Searching for the Missing on 085 209 2119 in strict confidence.