Comebacks are in vogue of late and Frank Lampard's Derby County produced a stunner of their own to keep alive their Premier League dream.
Trailing 2-0 on aggregate as the interval approached and, with a partisan Elland Road bouncing, Lampard's side looked to be nearing the end of their season, while Marcelo Bielsa's Leeds were heading for Wembley.
But come the end it was Lampard thinking about promotion in his first season in management after Jack Marriott's late winner stunned the locals. For Leeds, their absence from the Premier League will enter a 16th year.
It was Marriott who got the comeback going with a goal just before the break and, come the hour, Derby were leading 3-2 on aggregate after a strike from Mason Mount and a Harry Wilson penalty.
Casilla 5; Ayling 6.5, Berardi 4.5, Cooper 5, Dallas 8; Shackleton 6.5, Phillips 7, Klich 7; Hernandez 6.5, Bamford 5, Harrison 6.5
Subs not used:
Peacock-Farrell, Jansson, Struijk, Gotts, Bogusz
Dallas (23, 62)
Hernandez, Phillips, Bamford, Cooper, Berardi
Marcelo Bielsa 7
Roos 6; Bogle 6, Keogh 7, Tomori 6, Malone 6.5; Holmes 5 (Marriott 44, 7), Johnson 6.5, Mount 7.5; Wilson 7, Bennett 6.5 (Huddlestone 59, 6), Lawrence 7
Subs not used:
Carson, Jozefzoon, Marriot, Evans, Knight
Marriot (44, 85), Mount (46), Wilson (58)
Tomori, Malone, Lawrence, Mount
Frank Lampard 7
Anthony Taylor 7
Leeds levelled through Stuart Dallas - his second of the night - and we looked set for extra-time until Marriott's lovely clipped finish five minutes from time.
The first half had been as fiery as you would hope, six yellow cards just one shy of the total from Saturday's first leg. Not that we needed a reminder, but there is no love lost between these two.
The sight of 36,000 Leeds scarves being whipped in a frenzy in the seconds before kick off - the club had placed one on each seat - served to intensify an already heightened atmosphere. It was some sight.
Given the stakes, it was a bold call from Bielsa to include teenager Jamie Shackleton from the off, the midfielder making his first start since January and just his seventh at senior level.
But perhaps the more significant news for Leeds was the absence of first-leg match-winner Kemar Roofe, the 15-goal striker missing due to a calf injury.
That meant an immediate recall for Patrick Bamford after the expiry of his two-game ban for successfully deceiving the match officials during the stormy 1-1 draw with Villa last month.
But there was no doubting the foul on Bamford as he skipped clear on five minutes only to be tripped by Fikayo Tomori. The defender was spared a straight red by a recovering colleague, but the incident had set the tone.
There was some decent football played amid the madness. Leeds right back Luke Ayling started one move from his defensive post before charging upfield and connecting with Mateusz Klich's cross. It would have been a late contender for goal of the season had he scored. As it was, Ayling volleyed 10 feet over the crossbar. Back to right back he went.
But fellow full back Stuart Dallas made no mistake when he fired Leeds in front on 24 minutes after Kalvin Phillips' free-kick had crashed into the post and rebounded to the defender six yards out.
Out came the scarves and, with it, a rendition of 'Stop crying Frank Lampard'. But the Derby boss was laughing come half-time after seeing substitute Jack Marriott score with his first touch following a mix-up between home skipper Liam Cooper and goalkeeper Kiko Casilla, allowing the striker to roll into an empty net.
Still, no need to panic, the team finishing third in the Championship had not lost at home in the play-offs for nine years. Except panic is exactly what Leeds did.
Within 38 seconds of the second half Mount had levelled the tie as he jinked clear in the area before chopping home despite an untimely stumble.
Cooper, usually so dependable, was proving a worry for Bielsa and his centre-back conceded the penalty - needlessly tugging the shirt of Mason Bennett - from which Wilson slotted Derby into a 3-2 aggregate lead.
But back Leeds came and Dallas wriggled free before locating the bottom corner from 15 yards just after hour.
The noise that generated appeared to give the home side the advantage but that edge was taken away when defender Gaetano Berardi was sent off on 78 minutes for a needless lunge, earning him a second booking.
Lampard urged his men forward rather than settling for an additional 30 minutes and they thought they had won it when Wilson prodded against the post with six minutes remaining.
The Rams boss spun on his heels and buried his heads in his hands after that missed opportunity. But within 60 seconds he was spinning back towards his dugout in glee after watching Marriott keep his cool to lift into the far corner from 10 yards.
Lampard was mobbed by his coaching staff and he may well need a new suit for Wembley given the ragged fashion in which he emerged from their celebrations.
There was still time for some late nerves when Derby defender Scott Malone was dismissed, but those were forgotten on full-time as Lampard stormed the pitch to celebrate with his comeback heroes.