This was quite simply brilliant from East Fife.
Few outwith the Bayview dressing room would have given them much of a chance at Tannadice on Tuesday night - but how wrong they all were.
From the first whistle Darren Young's side got in the faces of their hosts who were rattled and never looked comfortable throughout the rest of the 90 minutes.
Scott Agnew, Liam Watt, Anton Dowds, Ross Dunlop, Aaron Dunsmore...you could list them all, everyone put in a shift that did the part-time club proud.
As a reward, just as other Fife teams have done at grounds like Pittodrie down the years, they picked up a result they'll never forget for the rest of their careers.
The Methil men arrived looking to build on a confidence boosting, and deserved, 2-0 win over Stenny on Saturday.
Robbie Neilson's side have made a blistering start to their Betfred Cup campaign, drawing one and then winning the other two of the three matches already played.
Darren Young rotated his squad from the weekend, handing starts to Ryan Wallace, Watt and Ross Davidson.
East Fife settled into the game well and had the better of the opening exchanges.
Starting with an attack minded front two, they pressed high and Agnew's through ball almost played Wallace in on goal but the striker just couldn't bring down the pass.
The Fifers were revelling on the large surface and had another great chance to open the scoring when Ross Davidson robbed the United defence on the edge of their own area.
He teed up Dowds but the striker couldn't keep his shot down.
United remained a threat on the break but it says everything about how the Fifers started the first half hour that that was the only threat they posed.
Scott Agnew was comfortable in possession as he poked and prodded balls through to Wallace and Dowds.
Down the right, Stewart Murdoch was playing with all of the intensity you'd expect of someone looking to prove a point to his previous club.
It was safe to say the opening goal was merited when it arrived on 38 minutes.
Dowds picked up the ball deep inside the United half and cut open the home defence with an excellent through ball which found Dunsmore.
The midfielder raced in on goal and calmly picked his spot beyond Benjamin Siegrist.
United responded straight away and were unlucky not to draw level a couple of minutes later when Lawrence Shankland cracked the bar from inside the box.
The expectation was that United would respond after the break, fly out of the traps and camp themselves inside the Fife half.
In fact, the opposite was true.
East Fife started where they had left off, and within five minutes of the re-start added to their lead.
Watt picked up the ball on the wing and was short of options inside the box.
He decided to go himself and raced in on a United defence which was guilty of not getting a foot in.
Watt punished them by curling an excellent effort out of the reach of Siegrist.
The game hit a lull, which the Fifers were grateful about, until United had a late flurry with 15 minutes left.
Shankland should have done better with a volley from six yards, but all the chance served to do with give the Bayview boys a wake up call.
They went straight up the park and Chris Duggan, Danny Denholm and Dunsmore all had chances.
It was 2-0, but could have been a lot more.
Bayview boss Darren Young said: "We have guys who have been at work since 8 until basically kick off time.
"The result is testament to them because they're a good group of guys who want to improve and progress.
"It was an outstanding performance from start to finish.
"We made four changes from the weekend and it says a lot about the squad that we can bring four guys in and put in a performance like that."