Airdrieonians mounted an absolutely sensational comeback to stun Montrose and book their place in the Championship play-off final after a 10-goal thriller.
The Diamonds trailed 1-0 from the first leg after Craig Johnston's strike gave the Angus side a slender advantage and found themselves 3-0 down in the tie before the most unbelievable scenes at New Broomfield.
Cammy F Ballantyne's first half brace looked to have put Montrose - who finished a huge 13 points behind Airdrie in League One this season - well on their way to booking a place in the final.
However, Airdrie produced comeback for the ages with Callum Smith netting a second half hat-trick in between a Lewis Milne strike for Montrose, before Calum Gallagher's 87th minute strike forced extra-time.
In the additional period, Jon Afolabi struck in first half stoppage time before Gabby McGill's goal proved decisive in the second half, after Martin Rennie netted a late goal for Montrose to see Airdrie prevail 6-5 on aggregate.
Airdrie now face Queen's Park over two legs in next week's final.
The Diamonds made one change from the first leg as Scott McGill stepped up to take the place of his namesake Gabby in the starting 11. And there were two alterations for the Gable Endies as Cammy F Ballantyne and Lewis Milne came in for Blair Lyons and Mark Whatley.
Just 40 seconds into the clash the Diamonds were looking for a penalty when Rhys McCabe's long throw from the right came to Callum Smith in the six-yard box. The striker went down under pressure from his marker but referee Alan Newlands waved away his appeal.
Two minutes later a second penalty appeal from the hosts was turned down when another McCabe throw caused havoc. The ball struck Cammy F Ballantyne on the arm, however the appeals fell on deaf ears once again.
Montrose keeper Allan Fleming was forced into action eight minutes in when Calum Gallagher cut inside and unleashed a powerful drive that Fleming did well to turn round the post.
But just as Stewart Petrie's side did in the first leg, they bagged an early goal to take control. Cammy Ballantyne burst down the left and his cross to the back post found namesake Cammy F Ballantyne, who towered above the Diamonds defence to power home a header with 12 minutes on the clock.
And things only got worse for the hosts in 26 minutes. Once again Montrose were allowed the time to get a cross in from the left and Cammy F Ballantyne was on hand to grab his second of the day, poking the ball into the net from Lewis Milne's delivery.
Airdrie responded by making a double substitution, with Scott McGill and Kyle MacDonald being replaced by Gabby McGill and Craig Watson on the half hour mark.
Moments later Callum Smith came close to pulling one back when his thunderous low drive forced Fleming into a great stop and then Johnston was denied by a superb goalline clearance by Cammy Ballantyne on the stroke of half-time.
The deflated Diamonds trudged off to a few boos from the home support at the break but they came out the blocks well in the second half as they sought a way back into the contest.
In 52 minutes Dylan Easton came agonisingly close to pulling a goal back when his sizzling strike from 25 yards crashed off the crossbar.
And just seconds later Smith got the goal they craved when he got into the box and fired a low strike in off the post to reduce the deficit to two goals on aggregate.
That goal had Airdrie in the ascendancy for the first time in the match but Montrose broke upfield in the 69th minute and restored their three-goal lead in the tie when Lewis Milne rifled home at the back post after being picked out by Johnston.
It looked like game over then but Airdrie had an almost instant response. Murray subbed on Jon Afolabi and the Celtic loanee teed up Smith with his first involvement, allowing the striker to curl in his second of the game and get Airdrie back to within two goals of forcing extra-time with 20 minutes remaining.
Incredibly, Smith struck again in the 75th minute to bag a second half hat-trick, arrowing a strike into the bottom corner after McCabe's delivery to leave the Diamonds needing just one to get back level in the tie.
Montrose were defending for their lives, trying to cling onto their advanatge but Airdrie's pressure told again in the 87th minute. After a bit of pin-ball in the box, Gallagher used his knee to turn home Afolabi's cross and, unbelievably, get Airdrie level to force extra-time.
It took until stoppage time in the first-half of extra-time for Airdrie to go ahead in the tie for the first time. And Afolabi was the coolest man in New Broomfield as he stroked a composed curling strike into the bottom corner from the edge of the box to spark incredible scenes.
Airdrie still weren't done though and completed the most monumental of performances in the 120th minute when Gabby McGill rifled home their sixth goal of the game.
Even then, Montrose weren't done as Martin Rennie netted in stoppage time but Airdrie held out for a sensational victory.
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