Every time Denis Walsh snr reads a news report of a discovery of a dead body, be it in Ireland or anywhere else in the world, he rings his local garda station in anticipation it may be his missing son's remains,
Denis jnr, aged 23, left his family home in Caherdavin, Limerick, 21 years ago today, March 9, 1996.
"Every time I see a report of a dead body, I ring the gardaí. The bodies of five Irish men were discovered in London one time, but they were all identified," said Mr Walsh, (78).
Speaking at their home, Mr Walsh and his wife, Mary, made an emotional plea for help in tracing Denis jnr, their youngest of five children.
With tears welling in his eyes, Mr Walsh said: "We got up this morning and went to mass and said prayers for him. We have to keep going. If you just sit at home it plays on your mind all of the time."
Still holding out hope after over two decades of searching for their son, he made another desperate appeal for help: "Somebody knows something. Anyone with information could contact a garda station; or a priest; or a friend; a social worker...they don't have to identity themselves in any way."
Mary Walsh described the family's ordeal as "terribly hard".
"We think of him first thing in the morning and last thing at night. He's always on our mind," she said.
"It never goes away."
In a direct appeal to Denis jnr, should he be reading this appeal, his devastated parents said: "Just contact us whatever way you can, even if it is just to send a card...just to say 'I'm happy'."
"We'd dearly love you to come home, but if that's not possible we just want to know that you're alive.
We just want to know that you are out there," Mary Walsh added.
Mr Walsh broke down as he made the appeal: "Come home, come home, there is always a welcome..."
The Walsh's said their beloved son suddenly "changed" from being sporty student who was holding a part-time job, to becoming withdrawn and depressed, after returning from a trip to Holland prior to his disappearance.
Denis jnr began taking drugs, and his mental health deteriorated, leading to him being hospitalised several times, they said.
"It's the one regret we have; that he went out to Holland and he came back a changed young man.
"It's unreal what (the drugs) did to him," his mother added.
There were positive sightings of Denis jnr in his native Limerick four days after he last left his home, and despite his parents travelling to Belfast, Birmingham, London, and the Isle of Man, after a number of reported sightings of their son, the trail has run cold.
Mr Walsh said: "I would take it that somebody knows something. We don't know (if he is dead)."
"If he was taking drugs and he owed drug money...you don't know what goes on; but we've never heard anything like that. We've heard other stories about other people but we can't confirm it."
Ms Walsh added: "We've nothing to go on now; There's nothing."
"We haven't found Denis's body and we have to assume the possibility that he is out there somewhere."
Anyone with information is asked to contact Mayorstone garda station on 061-456980 or Henry Street garda station on 061-212400.