In July 1917, a 31-year-old recently widowed woman entered the waves at Skerries and began to swim.
Different versions exist about what subsequently occurred, but Maud Gonne put it succinctly in a letter when writing that Muriel MacDonagh "swam out to sea towards Howth and never returned. She was such a lovely girl".
In the popular imagination the Easter Rising's final casualty was James Connolly, executed on May 12, 1916. This ignores the fate of eight-year-old Walter Scott, shot when walking in East Wall during the Rising, who died in Mercers Hospital on July 5 - after history's gaze had moved on.
But it could be said that this distraught young widow of the executed poet, Thomas MacDonagh, was the Rising's last casualty. Muriel MacDonagh was in Skerries with her two children - and with other widows and children of executed leaders - for the temporary respite of a short holiday.
If ever a group of women needed collective support it was these widows. Three were pregnant when their husbands were shot and two miscarried afterwards. Muriel stood out among the gathering in Skerries as being among the least militant-minded.
Similarly, she stood out among her strong-willed sisters as possibly the least radicalised of the fiercely independent-minded Gifford sisters. These included Grace Gifford, whose marriage in Kilmainham Gaol to Joseph Mary Plunkett, hours before his execution, had entered folklore by 1917.
That Skerries holiday must have seemed low-key compared to Muriel's long childhood holidays, when her prosperous parents often decamped to the seaside with a bevy of servants from their large house in Temple Villas on Palmerston Road in Rathmines.
The Gifford children always stood out. Their father, Frederick, was an affluent Catholic solicitor. Their mother however was resolutely Protestant and the dominant force in the home: rigidly respectable and rigidly unionist. All twelve Gifford children were raised as Protestants. The six sons retained unionist beliefs and led respectable, unremarkable lives.
In contrast, all six Gifford daughters rebelled against their mother's beliefs. In different degrees they embraced a radical tide of new ideas about nationalism and the rights of workers and women.
Grace - a talented artist - is now immortalised in Jim McCann's popular song, Grace. While deeply moving about the circumstances of her marriage, the song conveys little of the struggles of her later, impoverished life.
While Grace and Muriel were important witnesses to the Rising, their elder sister, Helen Gifford Donnelly - known as Nellie - was the only Gifford to play an active role in it, as the sister most actively engaged in radical politics.
The two social milieus in which she moved came brilliantly together during the 1913 Lockout. It was Nellie Gifford who booked a room in the Imperial Hotel in O'Connell Street, pretending to be the respectable niece of an elderly clergyman.
When this clergyman threw off his disguise and stepped onto the balcony, he revealed himself as Jim Larkin and delivered a speech to workers gathered below, despite being banned from doing so.
But while Nellie was the most politically active and another sister, Sydney, became a campaigning journalist (using the name 'John Brennan'), it is Grace who remains locked in the public imagination.
No marriage that is only allowed to last three hours can expect a happy ending, but her husband could not have predicted how impoverished and marginalised her final decades would be.
No two sentences better display the sad dichotomy between romance and reality than the description left by her sister-in-law, Geraldine Plunkett, of visiting Grace soon after the Rising: "When I went into her bedroom I saw a large white chamberpot full of blood and foetus. She said nothing and I said nothing."
Initially disowned by her own mother, Grace met an even more formidable foe in her mother-in-law, Countess Plunkett. This vindictive, rack-renting owner of numerous Dublin properties spent years fighting to deny Grace the inheritance bequeathed to her in Joseph Mary Plunkett's will.
Having taken the anti-Treaty side, Grace received only a measly state pension. She lived in a small flat near O'Connell Street, eating in cinema restaurants.
The government gave her a military funeral in 1955, but it was small compared to the crowds at her sister Muriel's burial in 1917.
Dubliners were given no chance to bury the 1916 leaders, but here was their chance to pay their respect to one of the widows.
Nobody knows what Muriel's intentions were when entering the waves. A story was quickly spun that she had wished to plant a tricolour on an nearby island. But perhaps this widow, who suffered several previous nervous breakdowns, could cope with her grief no longer.
She deserves to be remembered, not just in her own right and for the hardships endured after her husband's execution - when British soldiers callously rendered her house uninhabitable - but as part of a group of remarkable sisters.
They were six young women who turned their back on safe respectable lives to embrace revolutionary ideals - no matter what personal cost.