It could have been the greatest day. Instead, it provided one of the best ever 45-minute performances from an Irish team. They set a pace which they were unable to sustain and finished with 10 men.
There were moments that planted a false sense of security. Moments where it seemed as though the oldest team in the tournament, populated by players who could start next season in England's second tier, were on the verge of shaking the competition to its foundations by knocking out the hosts.
The prime example came in the 56th minute, just after Darren Randolph pushed a Blaise Matuidi shot away for a corner. It stirred the anxious crowd in Parc Olympique Lyonnais, allowing them to find their voice again. The Republic had led from the first minute and defended stoutly.
So the French sensed a turning tide and the volume rose. Dimitri Payet's corner was cleared by Shane Long. His return cross was dispatched to safety by Richard Keogh. In the attempted follow-up, Antoine Griezmann accidentally deflected the ball back up the pitch and into his half.
The majority of the 56,000 crowd groaned. Within 10 minutes, Griezmann had scored twice, Shane Duffy was sent off and the tie was over. So near, and yet so far.
"We look at the goals," sighed Martin O'Neill afterwards. "And we think, another six or seven minutes without conceding and we could have used that to our advantage if they were getting panicky."
France will have a week to prepare for a quarter-final with England or Iceland.
During the week, Irish players had spoken about the dramatic progression to the round of 16 as the stuff of dreams.
After 61 seconds, it had graduated to another worldly experience. France didn't touch the ball after the Republic kicked off. Stephen Ward was sharper than the ponderous Griezmann and sent in a cross that allowed Daryl Murphy to cause chaos and Long pick up the scraps in such a way that Paul Pogba illegally halted his path.
Referee Nicola Rizzoli pointed to the spot. Robbie Brady found his destination. France chipped away in search of a leveller but the siege lacked ammunition. Irish bodies threw themselves in the way.
The Republic were at full tilt, yet there were signs that it was catching up on them. Long was operating at half-pace after a lengthy stoppage and Jeff Hendrick was struggling too.
Half-time was needed for survival, but the lingering frustration is that the white shirts laboured when a clinical outfit might have nicked a second.
Didier Deschamps brought on Kingsley Coman, for N'Golo Kante, for the second period and with pace, they hit the Republic where it hurt. In the passage after Griezmann inadvertently ended one attack, the Atletico Madrid man ghosted towards the area.
James McCarthy missed him slipping in behind as Bacary Sagna curled over a cross. Griezmann's bullet header found a way past Randolph.
The second goal was much worse. Keogh was contesting with Olivier Giroud but Duffy got dragged across and caught in no-man's land. The Arsenal man's flick paved the way for another Griezmann dagger.
Last rites were served when McClean wasted a good opportunity and Les Bleus broke to demonstrate their class.
Giroud was stronger than Keogh and released Griezmann, who was scythed down by Duffy and Rizzoli inevitably flashed a red card.
There was no way back. Shay Given and Robbie Keane said nothing about future plans, but their actions spoke louder as they waved to the crowd.
O'Neill added: "Our younger players have come of age. Hopefully, it's just the end of the beginning."