Like most people, I knew the Titanic story as a gripping mosaic of disaster and survival - a roll call of what-ifs and might-have-beens told and re-told in film and book form for almost 100 years.
Endlessly fascinating, endlessly open to interpretation, endlessly emblematic of mankind's vanity and ambition, but also of our ability to behave with courage and honour in the mouth of the abyss.
What I didn't know is that I have a family connection with the Titanic. And when I discovered it - quite by chance - it was as if a switch flicked on and history stepped out of the shadows. The Titanic story became humanised on an intensely personal level for me.
Three years go, I stumbled across the fact that my grandmother's uncle was a passenger on the Titanic. And he was eloping to the US to start a new life.
He died on the maiden voyage of the vessel known as the Wonder Ship and his body was never recovered - but the woman he loved survived and had his posthumous baby.
It was almost a cliché. But it was also extraordinarily moving. And it had happened to a man just three generations removed from me.
I discovered his photograph and gazed at it, mesmerised. I'd always heard it said writers need look no further than their own families for stories - and here was the proof.
I fancied, staring at that grainy black and white image, that I could detect a family resemblance on my mother's side.
He reminded me of uncles and cousins. I could hear his voice speaking with their rich Munster intonation.
I tried to read the expression in his eyes and decipher what manner of man he was - gentle, impulsive, light-hearted?
Above all, I had the strongest sense of blood calling to blood.
So I made up my mind to tell his story - not as history, not as fact, but as fiction.
The version of events my imagination suggested, since this man had lived and died 90 odd years ago and there was nobody alive who remembered him. I decided to write Ship of Dreams and dedicate my novel - our novel - to him. My great-granduncle.
And there were two other people's stories I wanted to set down: Hannah Godfrey, the woman with whom he eloped, and Marion O'Brien, their baby.
She was present on the Titanic in embryo form. But she grew up without a father because a ship dubbed unsinkable steamed too fast through the iceberg region on her maiden voyage.
That mistake - one of hubris, perhaps - on the part of her owner the White Star Line and the Titanic's captain EJ Smith (he went down with his vessel and automatically became a hero) had made widows and orphans of many. I couldn't tell all those stories but I could give voice to Tom, Hannah and Marion's.
This is what I knew. Tom O'Brien from the townland of Bonavie in Co Limerick worked in a creamery. He was one of a family of eight, the son of a tenant farmer.
In 1912 at the age of 26, Tom decided to emigrate. It wasn't an unusual decision: all the young and able-bodied were bailing out; it was said of the Irish that we reared our children for the export market.
Tom had four sisters in Chicago and one of them acted as sponsor for him. It's a safe assumption the dollars for the journey came from the US too.
The four sisters, one of them my great-grandmother, were eagerly looking forward to his arrival. But Tom neglected to mention he wouldn't be travelling alone.
Whether it was a spur-of-the-moment decision or had been planned for some time we don't know, but he eloped with a girl from the next townland.
Together they made their way to Cobh, then known as Queenstown, and bought a steamship ticket to New York for £15 and 10 shillings.
And here's where chance or fate or just plain bad luck intervened. The liner Tom and Hannah were due to travel on had its sailing called off - it was a time of cancelled crossings because the steamships were reliant on coal and the Welsh miners were striking for minimum pay.
The couple had their tickets transferred to the next available crossing. And the ship that was to take them on their journey to the New World was the Titanic.
It must have seemed like an amazing stroke of luck, because everyone was talking about the liner: millionaires and movie starlets were travelling on the White Star Line's pride and joy.
And so were third class emigrants hoping to build a new life in the United States.
The Titanic had been built at the Harland and Wolff shipyard and a team from Belfast was also sailing to New York on her to check the steamship's performance.
Shortly before midnight on April 14, 1912 the unthinkable happened and the Titanic hit an iceberg. She sank in little more than two and a half hours - it happened so quickly there wasn't even time to launch all her lifeboats.
Tom O'Brien was among more than 1,500 souls who perished in the icy Atlantic waters. All of the Harland and Wolff men also drowned.
But Hannah was more fortunate. She escaped in one of the last lifeboats to be launched and made it to New York.
Just one in three of those who sailed on the Titanic were saved, and despite later insistence on how the 'women and children first' rule of the sea had applied, more first class men than third class children survived.
As for the Titanic, this marvel of marine engineering split in two and sank to the ocean floor, where she was to lie undiscovered until 1985. I like to believe that Tom O'Brien lies somewhere on the seabed with her.
Five months later, in September 1912, Hannah gave birth to his daughter Marion.
I said earlier I had discovered the little I knew by chance. I was doing some research on the internet for a different book about emigration and stumbled across the passenger list for the Titanic.
Idly running my eye down it, a name and address leapt out: Thomas O'Brien of Bonavie, Co Limerick. My grandmother, Josie English née O'Brien, came from Bonavie. It's such a small townland (near the Tipperary border) that I assumed there had to be a connection between the two.
"Did Granny have a relation on the Titanic?" I asked my mother. Her forehead pleated. "That's ringing a vague bell," she admitted. "I don't know anything much about it, just that there's a family connection. We knew never to talk about it as children. It upset your granny too much."
Why was he never mentioned? I learned there was a question-mark over whether Tom and Hannah had married - no record of a ceremony was found in Ireland - but surely this wasn't enough to explain the silence.
Then I got my hands on my Irish Independent colleague Senan Molony's non-fiction book The Irish Aboard Titanic.
It told how Tom's sisters had offered Hannah a home in Chicago but she had refused to leave New York, saying she'd be reminded all the time of Tom.
There was also a copy of a letter from Hannah to Tom's sister Mary O'Brien Hunt in Chicago (my great-grand aunt).
And the mystery was explained. Contact had been broken off between Hannah and Tom's family in a row over the compensation from White Star.
Both Hannah, who always insisted she was his wife, and the dead man's mother in Ireland claimed compensation as next of kin.
Hannah obviously produced some kind of proof in the US because the money went to her - as it should, in any case, with a child to raise alone.
This letter caused so much consternation that Mary forwarded it to Ireland for her mother Margaret to shake her head over. In it, Hannah accused the family of only being interested in the money.
"You needn't worry about me. My baby and myself will be alright. I knew ye were all trying to get some money. I produced my marriage certificate, and I had the nearest claim. So you nor the lawyer needn't bother," she said.
I wondered what had happened to her afterwards, but heard conflicting accounts.
And then I set aside the hunt to trace her and Marion's story, because by now I had embarked on the novel and wanted to write the version of events my imagination suggested.
Where I knew facts, I'd be obliged to use them. Not knowing gave me freedom.
I took as my starting point a pregnancy, an elopement and a death from drowning aboard the world's most famous ship.
What struck me during research was how, the more I read about the sinking, the more it became clear how little the aftermath figured in fiction or film.
It began to interest me increasingly. If you survived the Titanic sinking, what then? Would your glass be half-full or half-empty? Would you feel blessed or blighted?
And how had the steerage emigrants, many of whom survived in no more than the clothes they stood up in, managed once they reached the US? So I decided to write my novel about a group of Titanic survivors.
Then, too, I wondered if there was any interaction between the classes. Social hierarchies were rigidly adhered to in 1912. But what if, I speculated, people from diverse backgrounds met in a Titanic lifeboat.
Would their common bond as survivors be enough to overcome niceties about rank and accent?
Ship of Dreams was a labour of love in that I wanted to reclaim Tom O'Brien for the family.
I retuned again and again to that thumbnail picture of him and speculated about what ran through his mind as the ship foundered.
Did he know he was to be a father? Did he worry about what would happen to Hannah and their baby?
When I finished my novel, chance or fate or just plain good luck intervened.
Shortly before Ship of Dreams was published I finally made contact with the descendants of Tom and Hannah in the US and received answers to some of the questions I had about them.
I spoke to their granddaughter Catherine Hanlon Fisher, a lovely young-old lady of 70, mother of seven and grandmother of 11, who lives in Manchester, Tennessee.
Marion was her mother, and she told me about Hannah and Marion's lives in New York.
Hannah married a Co Kilkenny man named Jim Quinn when Marion was two or three, and had a son.
But she died just six years after the Titanic sank, in the flu epidemic of 1918.
The orphaned Marion was raised by her stepfather, who burned all her mother's papers after the funeral - so she had no way to contact her Irish relatives.
She was the family breadwinner at 14. In time she became a telephone operator in Brooklyn and married an Irish emigrant, civil engineer Willie Hanlon, also from Kilkenny, who was related to Jim Quinn.
They had three children and a happy life together in Albany, upstate New York.
When she was widowed after 40 years Marion moved to Tennessee to be near her daughter.
In her lifetime she avoided boats, was nervous of the ocean, rarely talked about the Titanic and resisted joining any Titanic societies.
Indeed, she only told Catherine about the family link when she was a young woman towards the end of the 1950s.
Later she visited Ireland and met some of her maternal relatives, but never made contact with any of her father's people. She thought we didn't want her. I still find that sad.
Marion died in 1994 at the age of 81, on Independence Day.
Most poignant of all was to learn that although Tom O'Brien never reached the US, he had three grandchildren and has nine great-grandchildren and 15 great-great grandchildren scattered around the States.
His descendants settled and prospered in the country he did not live to see.
In that, he achieved a version of immortality - despite his premature death in a seafaring disaster that echoes through the generations.
Ship of Dreams by Martina Devlin has just been published by Poolbeg, £10.99