Treacy on the double as Sky Blues deliver
Dublin 2-15 Offaly 1-10
At half-time in O'Connor Park, Dublin hurling's roller-coaster week was threatening to finish on a note of deflation in the Midlands, their U21s trailing Offaly by four points in this Bord Gáis Energy Leinster final.
Some 90 seconds after the restart, though, Joe Fortune's men were level and the trend for a second half of near-total domination had already been firmly established.
Seán Treacy delivered the killer blows with a brace of goals inside the first ten minutes but he was brilliantly assisted by Andrew Jamieson Murphy, who lit up the evening with four points from play, Jake Malone, who shot two from midfield, and Cian Boland, who delivered a lung-busting contribution off the bench.
And so it all finished in an emphatic eight-point triumph for the Dubs, who duly laid claim to their sixth Leinster title in the grade.
It also crowned a spectacular underage double, following just three days after their provincial minor success against Wexford ... not a bad riposte to the gloom that greeted Saturday night's agonising senior exit to Cork.
It was Dublin's first U21 title since 2011 whereas, for Offaly, the long wait goes on. They hadn't lifted the Seán Robbins Cup since 2000 but dared to dream that home advantage could tip the balance. That, and a lust for goals that had seen them raise five green flags in each of their matches en route. Only one problem: they weren't facing Kildare or Carlow here.
Dublin, meanwhile, had their own senior demons to exorcise, with the loss on Leeside still fresh in the memory of skipper Shane Barrett, Eoghan O'Donnell, James Madden, Chris Bennett and Treacy.
And they were soon playing catch-up, the hosts first out of the blocks with an early brace from Dylan Murray (free) and Johnny O'Toole-Greene, who caught the next Dublin puckout and promptly fired over.
Dublin drew level through a couple of Bennett frees; sandwiching those scores, the same player briefly threatened a goal when he outfielded Ben Conneely only for his marker to make a vital recovery hook.
Ultimately, there would be no repeat of his semi-final heroics from Bennett, who nailed four deadball efforts, made a couple of fine fetches but struggled to escape the limpet-like attentions of Conneely prior to his 44th minute departure.
Playing with the breeze, Offaly lined up with just two inside forwards against three Dubs but still made headway.
Emmet Nolan ignited their first half charge by winning possession and making a beeline for goal, drawing a 14th minute penalty and a yellow card for O'Donnell. Up stepped Oisín Kelly to bury the chance, and their three-point cushion then stretched to five via a Conor Doughan free and a Dylan Murray point from the wing after slick approach work by Pádraic Guinan.
Dublin didn't register their first point from play until the 28th minute, when centre-back Cian Mac Gabhann ghosted up the right wing onto a prodigious Jamieson Murphy line cut, firing over to leave a goal in it.
But then Nolan fired over a brace from play, with Bennett's injury-time '65' leaving it 1-6 to 0-5 at the break.
Offaly fans made up the majority in the 4,709 crowd, but they were silenced within 15 seconds of the restart by Jamieson Murphy's first point, and then after 90 seconds by Treacy's first goal.
Malone was the creator with a pass inside; the younger brother of David Treacy gathered smartly and his low, fizzing finish carried the hallmark of a predator.
Offaly briefly edged back into a two-point lead, but then another Jamieson Murphy point was followed by Treacy's decisive second goal on 40 minutes, the Cuala man catching Barrett's long delivery before kicking to the net.
He would add another two points from placed balls as Dublin outscored their faltering hosts by 2-10 to 0-4 in that second half.