Aaron Rowe scored twice as League Two side Crewe Alexandra bundled Derby County out of the FA Cup with a first-round replay win at Pride Park.
Tom Barkhuizen gave the League One hosts the ideal start with cool finish after just three minutes, but Rowe's first-half double - and first two goals for the Railwaymen - had the visitors on course for the upset.
Crewe goalkeeper Harvey Davies crucially tipped a Max Bird shot onto the crossbar as the Rams searched for an equaliser before the break.
Mickey Demetriou went on to add a third goal for Crewe with a second-half header to set up a second-round home tie against League One side Bristol Rovers.
Rams boss Paul Warne made two changes from the side that beat Barnsley 3-0 three days earlier in League One, while there were three changes for Crewe after they snatched a late win against fellow League Two high-flyers Notts County on Saturday.
And while it was the final moments of that league game that produced drama and controversy, this match got off to an exhilarating start with both sides scoring inside the first seven minutes.
Louie Sibley snatched possession from Crewe as they attempted to play out from the back, and set Barkhuizen up for an early opener for a Derby side that needed two late goals in the initial tie to force the replay.
But Derby's joy was short lived, with Rowe finding the bottom corner for the equaliser before Joe White demanded a fine save of Joe Wildsmith with a deflected free-kick.
Wildsmith could do nothing when a shot from Rowe took a heavy deflection off Eiran Cashin for his and Crewe's deserved second goal in the first half.
It took another excellent save from Wildsmith to keep Courtney Baker-Richardson from adding a third, while Crewe keeper Davies foiled James Collins and helped a Bird effort onto the bar at the other end just before the half-time.
Second-half chances were limited, but Demetriou managed to put the tie out of Derby's reach with a near-post header from a White corner with 25 minutes remaining.
Baker-Richardson and Shilow Tracey went in search of a fourth, but Wildsmith limited the damage on a miserable night for the Rams as they were knocked out in the first round of the FA Cup for the first time since the 1984-85 season.
Derby County head coach Paul Warne told BBC Radio Derby:
"I think we wanted the game, I just don't think we performed like we look like we wanted it.
"I explained to the lads before the game, if you turn up and you are in really good form - which the lads have been - and you turn up and think 'we will be alright tonight, we will just go through the motions' I warned them.
"I'm the oldest man in the dressing room, but I've played in these games, when you turn up and think, 'we will be alright', you can't and you can't turn it on after 15 minutes - you can't turn on the psychological jets on.
"Maybe that was a reason, maybe back-to-back games was too much physically for some of my players.
"They [Crewe] just looked like they had more in them, which is the nice way to put it."
Crewe Alexandra boss Lee Bell told BBC Radio Stoke:
"It's a really brilliant night for the football club, and I'm so proud to be part of it.
"I'm so proud of the players, the supporters were excellent. I thought it was right they won the game, the game plan was spot on and they executed it brilliantly.
"I've just said to the players that these past two or three weeks, with all that has gone on, the performance is the proudest time I've had in football.
"We will enjoy it tonight, I'll be having a beer on the bus."