Rory Beggan landed a free with the final kick of the match as Scotstown beat Kilcoo 0-12 to 1-8 in the Ulster Club Championship quarter-finals.
Paul Devlin's penalty had Kilcoo four points clear but Beggan's pressure kick completed a superb comeback.
Elsewhere, Glen marched into the semi-finals with a convincing 0-11 to 0-7 win over 14-man Cargin.
Cavan's Gowna are playing Donegal's Naomh Conaill in the final quarter-final tie.
Scotstown, who are looking for their first Ulster title since 1989, will face Tyrone's Trillick, who defeated Crossmaglen on Saturday, in the last four.
All-Ireland finalists Glen will face the winner or Gowna and Naomh Conaill in the last four.
In a remarkable turnaround at Paric Esler, Monaghan champions Scotstown produced a superb comeback from three points down with five minutes to play to beat Kilcoo with the last kick of the game.
The sides were level at 0-4 to 0-4 at half-time in a tight first half. It was Scotstown who struck first when some great work by Darren Hughes was finished off by Shane Carey.
Kilcoo hit back when Miceal Rooney and Darryl Branagan responded, and although Jason Carey pulled one back, Eugene Branagan soon restored the Down champions' lead.
Scotstown had a chance to level when James Hamill's long-range effort hit the post and landed the wrong side, and Kilcoo showed their clinical edge when Aaron Morgan raced up the other end to extend their advantage.
However, Scotstown dug deep and Shane Carey pulled one back before Conor McCarthy finished off a flowing move to bring the Monaghan men level at four points a piece at half-time.
After early scores by both sides, Kilcoo hit the front nine minutes into the second half when Ceilum Doherty was caught in the area and referee Noel Mooney awarded a penalty.
Devlin kept his cool to send his penalty down the middle, and further points from Seahlan Johnston and Anthony Morgan looked to have put the Down men in a strong position.
Rooney spurned a goal chance for Kilcoo when well placed in the square, and Scotstown began to chip into their advantage as the clock ticked down.
Jack McCarron struck twice and Beggan's free put one between the sides before Jack Carey levelled it in added time.
It looked like Kilcoo would have the decisive say when Devlin landed a straightforward free to put the former All-Ireland winners in front.
However, there was more drama to come when Kieran Hughes called for a mark and kept his cool to land a superb point, and Scotstown won a free from the kick out which allowed the ice-cool Beggan to land the decisive point with the final kick of the match.
Glen see of 14-man Cargin
Holders Glen edged out 14-man Cargin 0-11 to 0-7 at Celtic Park to reach the semi-finals of the Ulster Club SFC.
Tomas McCann was dismissed for the Antrim champions on 26 minutes after a high challenge which prevented Glen from launching a counter-attack.
These two sides met in last year's semi-final, with Glen winning by five points on their way to claiming the Ulster title.
Malachy O'Rourke's men made a blistering start to this game, with Jack Doherty firing home a point after just 12 seconds.
Danny Tallon added a quick-fire second score when he split the posts from a free before Ciaran McFaul would hit the first of eight wides the Derry side registered in the game.
A Pat Shivers free got Cargin on the scoreboard with Tallon replying with a free of his own.
Paul McCann reduced the deficit before Emmet Bradley got his first score of the day with a long range free.
Cathal Mulholland had a goal scoring opportunity on 20 minutes, but his effort from a narrow angle was blocked.
Shivers brought the game back to a point with another free in this entertaining and physical contest before Tomas McCann received a red card for bundling into Conhuir Johnston as he tried to break away.
Glen made their man advantage count, stretching their lead with Jack Doherty striding forward and pointing to take their tally to 0-5 at half-time.
They made an equally fast start to the second half as they did the first, with CMcFaul getting his first score of the day before Alex Doherty's strike forced Cargin's John McNabb into a sprawling save.
Bradley and Shivers exchanged frees with Mick McCann bringing the game back to two points for Cargin.
Michael Warnock and two frees from Bradley would help Glen pull away and establish a five point lead, but Cargin refused to give up as Kieran Close and McCann helped them to stay in touch.
Ethan Doherty curled home the final point of the game from a narrow angle to seal the hard-fought win for Glen.