Topi Keskinen's curling strike just before half-time saw improving Aberdeen stun leaders Hearts with a 1-0 victory at Pittodrie.
Keskinen benefitted from a significant ricochet before curling home a sweet strike.
Celtic's win over St Mirren had already cut Hearts' lead at the top to just four points, and the visitors were missing Lawrence Shankland due to a calf injury, and Craig Halkett through suspension.
Hosts Aberdeen had taken 10 points from 15 in their prior five league games as their form steadied, but they were without star man Jesper Karlsson due to personal reasons, one of three changes from their draw with Motherwell.
A pre-match downpour contributed to a first half contested at breakneck speed, often raging from end to end.
Jack Milne sent Keskinen racing up the park on an early counter, the Finn teeing up Stuart Armstrong. His shot was blocked, and Dylan Lobban's follow-up easily held.
Cammy Devlin's deep delivery should have been turned home by Stuart Findlay at the back post, but somehow the defender hit wide.
A similar delivery a few minutes later pinballed around the box, before Harry Milne, who again should have found the net, clipped the bar.
Set-pieces looked Hearts' best route to goal, and Dimitar Mitov was on hand to grasp a close-range Frankie Kent header after another corner, before minutes later diving at the feet of Pierre Landry Kabore as the striker took a loose touch.
On the half-hour, Claudio Braga appeared to go over the outstretched foot of Mats Knoester, but referee David Dickinson was swift to spot a dive and instead booked the Hearts man.
Play was relentless, but it would be the Dons who broke the deadlock. Dante Polvara lifted a smart ball over the top for Keskinen, who got a hefty break of the ball before curling low across Alexander Schwolow and into the far corner of the net.
The hectic pace continued after the break, and Mitov again had to be alert to block a close-range header, this time from Tomas Magnusson after more penalty-box pinball.
At the other end, Armstrong's half-cleared free-kick saw Polvara take a touch before sending an 18-yard effort narrowly over.
With 15 minutes to go, Hearts should have been level as Kabore got in behind and squared for Braga. Mitov was once again the hero, before Jack Milne cleared for a corner.
The visitors threw everything forward in search of a leveller but the Aberdeen defence held firm to see out a hard-fought win.
Hearts boss Derek McInnes:
"I thought we were decent throughout the game to be honest. If you don't take the chances here, if you don't show the quality and composure needed to win here at Pittodrie then you run the risk of losing the game.
"We didn't have too much to do defensively, but we lose the goal on a transition. We give the ball away 20-30 yards into their half, it's one pass forward and before we know it we're in a difficult position.
"We felt like we had good control in the game, particularly in the second half, stats don't matter if you've not got the quality. The boys have the quality, it's been on show all season, but they weren't quite on point.
"That's always going to happen, you're always going to lose a game. We thought we'd done enough today not to lose. I was actually quite encouraged by the performance today without Lawrence [Shankland] and Craig Halkett."
Aberdeen boss Jimmy Thelin:
"We are a hardworking team with a lot of good characters, and we had a lot of new players over the summer. The last six games, it's four wins, one draw and one loss. In a difficult situation, the players are showing a lot of spirit and responsibility.
"You always get what you deserve and a lot of players have grown in this context. If you can stay focused under a lot of pressure as the players have been, and I'm happy and pleased for the players because their hard work is showing.
"Topi [Keskinen] has played a lot before, but not so much in the last six games. Instead of complaining, he's been working hard and when the time comes he showed he wants to play.
"It's still early in the season and there's a lot of big games in front of us now. The thing is to be consistent.
"Today was a good game, really intense. Where the team really has grown is in not getting stressed when the opponent has a lot of momentum."
