Jed Wallace's injury-time strike handed Millwall an extraordinary 4-3 victory - their first on the road in the Sky Bet Championship in 2017/18 - over Leeds United at Elland Road on Saturday afternoon.
Goals from Aiden O'Brien and Lee Gregory put Millwall two to the good, but a double from Pierre-Michel Lasogga and a strike from Kemar Roofe swung the pendulum the way of the home side.
Tom Elliott equalised late on to seemingly secure a share of the spoils against 10-man Leeds, who had Liam Cooper sent off in the first-half, but Wallace struck in added-time to win the game.
Neil Harris made two changes from last Saturday's 1-1 draw with Preston North End, with Conor McLaughlin and Shaun Williams coming into the side at the expense of Mahlon Romeo and Ryan Tunnicliffe.
Shane Ferguson returned from injury to take his place on the substitutes' bench.
Millwall started well and could have had the lead after just 13 seconds, but O'Brien's curling effort was palmed away by Felix Wiedwald. The Lions were unaffected by the partisan sell-out Elland Road crowd and nearly nudged themselves in front again on four minutes, but O'Brien couldn't turn the ball home.
Seven minutes in, Lasogga fluffed his lines from six yards out, despite looking offside, with a free header that trickled into the arms of Jordan Archer. Lasogga once more should have opened the scoring on 13 minutes, but Archer saved well from the striker's tame effort.
In a game of chances, on 16 minutes, Gregory beat his marker but rolled his attempt agonisingly wide of the far post. A minute later, The Lions had the ball in the net as Wallace drilled home, but for a borderline offside on Steve Morison, the goal was disallowed.
Millwall put that right just 60 seconds later, however, as O'Brien headed home Morison's cross at the back post to send the away contigent - only just returning to earth from Wallace's strike - into raptures once more.
Leeds were unable to deal with the visitors' attacking power, especially from set-pieces, with the goalscorer nearly doubling his tally on 25 minutes as he flicked Wallace's free-kick on to the roof of the net. Jake Cooper also headed wide as the efforts on goal tally continued to rise.
Shaun Hutchinson hit the crossbar with a header on 33 minutes in yet another Millwall attempt on goal - by now, The Lions' dominance should have been reflected on the score-line and Harris' side should have been out of sight.
Leeds captain Cooper was sent off for a reckless challenge on George Saville with 36 minutes on the clock.
Rattled by The Lions' dominance, Leeds were beginning to lose their discipline, with Pontus Jansson going into referee David Coote's book for bringing down Saville in cynical fashion.
The afternoon turned just that little bit sweeter for Millwall a minute later, as Gregory bundled home Morison's cross from close range at the back post. In first-half stoppage-time, Wallace's drive across goal was turned behind for a corner-kick.
The second-half was merely 23 seconds old when The Whites halved the deficit, as Lasogga powered an effort into the corner of the net.
An amazing Sky Bet Championship encounter continued to ebb and flow, with Wiedwald expertly plucking a goal-bound Gregory header out of the sky with 53 minutes on the clock.
That proved to be telling as a minute later, after an almightly scramble inside the six-yard box, Roofe stabbed the ball over the line to even the scores.
On 62 minutes, Lasogga drove home with an impressive strike to put Leeds into the lead. Substitute Elliott headed wide five minutes later as The Lions tried to find a way back into the game.
On 76 minutes, a bout of pinball saw the ball eventually go behind for a Leeds goal-kick after efforts from a number of Millwall players were blocked.
Millwall still pushed forward for the equaliser but found a stubborn United defence in the way of shots from Saville and McLaughlin.
However, with three minutes remaining, Elliott controlled well and slotted home to put The Lions back on level terms.
With the game in stoppage-time, Wallace ran at the Leeds defence and fired a deflected shot into the net to send the travelling contigent into delirium - The Lions had finally clinched the away win that their play over the course of the campaign had more than deserved.
Leeds United: Wiedwald, De Bock, Jansson, Cooper, Berardi, Phillips, Vieira (Pennington 43'), Alioski, Hernandez, Roofe (Dallas 74'), Lasogga (Shaughnessy 83'). Subs not used: Lonergan, Anita, Cibicki, Sacko.
Scorer: Lasogga 46' 62', Roofe 55'
Booking: Jansson, Alioski, Phillips
Sent Off: Cooper
Millwall: Archer, McLaughlin (Romeo 82'), Meredith (Elliott 66'), Hutchinson, Williams, Gregory, Wallace, Morison, O'Brien (Ferguson 63'), Saville, Cooper. Subs not used: Martin, Craig, Tunnicliffe, Thompson.
Scorer: O'Brien 18', Gregory 42', Elliott 87', Wallace 90+2'
Booking: Hutchinson, Elliott
Referee: David Coote
Attendance: 33,564 (1,285)