Cavan and Donegal will stage a repeat of last year's Ulster final after Mickey Graham's men overturned an eight point half-time deficit to stage another smash and grab.
The Breffni men were seven points down against Monaghan in the preliminary round and they clearly have a tendency to make life hard for themselves.
"What you see with these lads is what you get," said a beaming Graham afterwards.
"They are never going to throw in the towel. A lot of teams that found themselves in the situation we found ourselves in the last three games, they might tap out. But these boys just keep going and going and going. And you have to admire them for that, it was just pure willpower from them today and they never gave up."
The weather conditions were always going to have a huge effect on some of these Ulster matches and it was the case here. Not because there was a wind aiding Down as they careered into a 1-9 to 0-4 lead by the break, but because their pace and handling was so much smarter.
Down had a goal when Jerome Johnston laid off to Ceilum Doherty to smack home and had further goal chances when Johnston - who was riding high on confidence after a series of brilliant points - was blocked down by a superb Padraig Faulkner full length dive.
The other came when Caolan Mooney's pace took him beyond the Cavan cover with a soccer dribble, but Raymond Galligan was equal to it.
Playing their fifth game in five weeks, following league outings against Roscommon and Kildare, and Championship encounters with Monaghan and Antrim, Graham's men looked leggy and tired. The heavy pitch took a toll while Down looked far more full of energy.
The late introduction of Liam Kerr by Down boss Paddy Tally was a clever move, given the Burren man's raw pace against a tired rearguard.
But when Cavan got into their huddle at half-time, they made some key adjustments. Thomas Galligan was put in at full-forward and denied Down their sweeper in Kevin McKernan.
Conor Madden came on at the break and scored three points from play and set up two other points.
Graham also pushed Faulkner into a more advanced midfield role after the break and they just swamped the middle thereafter.
No fewer than 10 of Down's 14 kickouts were claimed by Cavan in the second half, Mourne goalkeeper Rory Burns being put under savage pressure.
While Down only scored four more points, they couldn't get their game going whatsoever. They still spurned a glorious goal chance on 40 minutes when Mooney's pace took him through and, while he was passing to the unmarked Paul Devlin, Conor Poland appeared to come out of nowhere to attempt a diving fist, but only steered it wide.
Cavan's comeback got under way in earnest a minute later when Martin Reilly tucked away a penalty after the umpires adjudged Kevin McKernan to have touched the ball on the ground.
It wasn't a decision that met with the approval of Down boss Tally.
"It was a very controversial call," he said.
"It was made by the umpire - the referee didn't make a call on that and an umpire made a call on a penalty? I've never seen that before. I've never actually seen an umpire make a decision on a penalty.
"Linesmen don't make calls, umpires don't make calls, but we get an umpire today makes a call on a penalty? That's not within the rules that an umpire makes a call on a penalty or not.
"That, to me, was a poor decision."
From then on, a steady stream of points carried them home, McKiernan exerting an ever-growing influence as the game went down the stretch.
Down could not get momentum to swing back in their favour. On a still day, albeit with a bitter light rain falling, they went 10 minutes between their first and second points - and 20 minutes between their second and third.
Both teams were gripped by white line fever.
From the hour mark, Madden twice and Ciaran Brady came forward and kicked wides.
Down will rues missed chances, but this was a failure of composure.
Scorers for Down: J Johnston 0-6, 1m, D O'Hare 0-4, 3f, C Doherty 1-0, P Devlin 0-2, 1x'45'
Scorers for Cavan: G McKiernan 0-3f, T Galligan 0-3, 1m, M Reilly 1-0 Pen, C Madden 0-3, K Brady 0-2, P Faulkner, C Brady 0-1 each, S Smith 0-1f
DOWN: R Burns; P Fegan, P Murdock, P Laverty; L Kerr, K McKernan, D Guinness; C Mooney, J Flynn; B O'Hagan, P Devlin, C Poland; J Johnston, D O'Hare, C Doherty.
Subs: S Johnston for Kerr (49m), D Ward for Devlin (51m), C Quinn for O'Hagan (57m), J Guinness for Poland (65m), R Johnston for D Guinness (67m)
CAVAN: R Galligan; J McLoughlin, P Faulkner, L Fortune; G Smith, C Brady, P Graham; K Clarke, K Brady; M Reilly, G McKiernan, O Kiernan; O Pierson, T Galligan, S Smith.
Subs: C Conroy , for Graham, C Madden 8, for Pierson (half-time), TE Donoghue for S Smith (51m), C Timoney for K Brady (60m), N Murray for M Reilly (69m)
Referee: Martin McNally (Monaghan)