Ten-man Hearts dropped three crucial points in the race for the Scottish Premiership title with a gut-wrenching 1-0 late defeat to St Mirren in Paisley.
The league leaders played for more than an hour with one fewer player after Craig Halkett's first-half red card and survived a barrage of attacks until Miguel Freckleton's emphatic 88th-minute winner.
The Jambos remain six points clear at the top but have handed chasers Celtic and Rangers the opportunity to close the gap on Wednesday.
Stephen Robinson's much-improved St Mirren earned a first league victory in eight matches, taking them 12 points clear of bottom spot as they move above Dundee into ninth.
Ultimately, the hosts deserved the win. They were the better of the two sides even prior to Halkett's dismissal.
But that was where early pressure turned into an onslaught.
The stand-in Hearts captain initially covered well for his defensive partner Stuart Findlay's mistake but then stumbled in possession himself before bringing down Jacob Devaney on the edge of the area to deny a clear goalscoring opportunity.
And the first-half drama did not stop there.
St Mirren captain Marcus Fraser had the ball in the back of the net, however, team-mate Alex Gogic was adjudged to be in an offside position when he headed the ball off the post to tee up Fraser's rebound.
Robinson's side then thought they had a penalty when referee Steven McLean pointed to the spot following Harry Milne's challenge on Jayden Richardson, but the decision was overturned by VAR as the foul took place outside of the penalty area.
Hearts stopper Alexander Schwolow was called into action again early in the second period as he produced an outstanding save with his right shoulder from close range to deny Mikael Mandron.
The visitors had seemingly weathered the storm thereafter but were unable to replicate the heroics of last month's back-to-back victories with a numerical disadvantage as Freckleton won it for the Buddies with a thunderous header from Declan John's corner two minutes from time.
Hearts may be just three points clear when they take on city rivals Hibernian next week. That is followed by a top-of-the-table clash with title-rivals Rangers on Sunday February 15 - live on Your Site.
St Mirren manager Stephen Robinson speaking to Your Site:
"It was more like us tonight. That's four unbeaten now, with two wins within that. We're starting to build a little bit more momentum again. We're starting to turn a corner. To put on a performance like that against the league leaders... it looked more like us. I thought we deserved it.
"We had a a lot of half-chances; it probably should have been by more. The sending off affects the game, but we were patient and managed to get the end product.
"The way we started was excellent. Our press was really, really good and we kept taking the ball off them. We missed two or three really good chances, the penalty was overturned - both of the decisions were right, actually. I've just seen them back. We criticise referees enough, but you've got to say when they've got it right as well.
"As I said, four games unbeaten. We've managed to win a cup this season, which I think people have forgotten as well. We have the chance to get into the quarter-finals of another cup on Friday night. The goal at the start of every season at this club is to stay in the division. The win tonight helps us do that."
Hearts manager Derek McInnes speaking to Your Site:
"Very [tough]. I thought we did what we had to do to get something out of the game, we're working harder than we want to by constantly going to down to 10 men but we've caused that.
"We've been unbelievable with our coping mechanisms going down to 10 recently but we're playing with fire if we keep doing it.
"No complaints about the red card. Our refusal to play forward gets us in a state. We knew St Mirren would try to come after us, the difference between our centre-backs and theirs was 30 yards but we refused to play in behind them.
"We got the game back to front. At times it was okay, we'd break the press and get through it, but we needed to play in behind us a lot more.
"None more so than the red card. We've had two opportunities to play forward, and we don't. We end up getting ourselves in a state, and it ends up with Halks having a last-gasp challenge. There's no blame on him for that.
"There's a consequence as well. You struggle here and try to salvage something from the game but there's a consequence, a knock-on effect about having a player suspended.
"There's no complaints about the effort of the team and what we tried to do to manage it. We've done it recently, the belief and confidence is there in the team to try to get something from the game but the galling thing is it comes from a set play where a numerical advantage shouldn't matter. We just got caught under the ball. It's a good header but a free header six yards from goal, we're playing with fire there too.
"Credit to St Mirren, they kept going and asking questions but by and large we dealt with being a man down brilliantly up until the dying embers."
