Martyn Woolford struck an 85th-minute winner as Millwall's promotion dream ended in a devastating defeat at Wembley Stadium.
In an epic encounter that was a credit to the third tier of English football, both The Lions and Scunny gave everything in sweltering conditions that saw temperatures top the 100 degree mark at pitch level.
This was a game that just about had it all - and a a sickening way to miss out having come within touching distance of promotion.
Having turned a 1-0 first-half deficit ino a 2-1 lead with just 20 minutes remaining, and the finishing line of the Championship in sight, The Lions were caught out by two sucker-punch goals that leave them facing another season in League One.
This time last year manager Kenny Jackett had already started planning for the 2008/9 campaign after The Lions had only just avoided relegation by the skin of their teeth with a 3-0 win against Carlisle United on the penultimate Saturday of the season.
There was no rest for Jackett and his backroom staff as players were targeted, brought in - some on loan, others permanently - and a strong, resilient squad took shape.
When Millwall kicked off the season with a 4-3 defeat at Oldham Athletic, having seen a 3-1 lead disappear in a matter of minutes following the harsh sending-off of defender Paul Robinson, the doom and gloom merchants were already convinced that the following nine months were going to be a long, anxious struggle against relegation.
But the spirit, resilience and sheer dogged determination of the players, along with a large portion of skill, saw Jackett's side win games they would perhaps normally have lost, beat sides that they were not given a hope against, such as Leicester away, and in 45 second-half minutes at Hartlepool when a Neil Harris hat-trick turned a 2-0 deficit into a stunning 3-2 victory as all those facets combined together.
This pack of Lions had pride, purpose and a clear target - promotion.
Anyone who had questioned Jackett's tactical nous, or the camaraderie amongst an incredibly tight-knit bunch of players, were left in no doubt as the unfancied Lions not only secured a place in the Play-Offs, but went on to make history by winning a first-ever Play-Off game at the ninth attempt with a 1-0 success against Leeds United.
The second leg tie at Elland Road saw a partisan 37,000 crowd stunned into silence when Jimmy Abdou scored 16 minutes from time, sparking wild scenes of celebration at the final whistle from the 900 travelling fans.
And so to Wembley, where Bermondsey as a community upped sticks for the day joining fans from all over the world who had travelled by boat, plane, train and double decker bus to proudly be part of a record-breaking 44,159 Millwall fans that turned the splendid stadium into a sea of blue and white, and rocked it to its very new foundations with an unbelievable wall of sound that started long before referee Michael Oliver blew to get proceedings underway bang on 1pm.
There were few surprises in either starting line-up, with Jackett bringing in Lewis Grabban for James Henry, whose loan spell from Reading had expired after that memorable night at Elland Road.
Scunthorpe boss Nigel Adkins welcomed back hitman Gary Hooper from injury - news that was met with by groans amongst the Lions fans when his name was read out before kick-off.
Hooper has had this uncanny habit of popping up with a goal or two against Millwall in recent encounters, you see.
But it was Grabban who had the first chance of the game after three minutes. A long upfield punt by Forde was picked up by Harris, who in turn weaved his way into the box before picking out Grabban, but the latter's header was held comfortably by Joe Murphy in the Iron goal.
However, within seconds it was Iron who drew first blood with their first penetrative attack into the opposition half.
Hooper and Paul Hayes combined on the left to set up Woolford in a central position. His shot was parried by Forde, but Matt Sparrow was quickest to react and slammed the ball into the roof of the net from five yards.
Scunthorpe were inches away from adding a second goal on 13 minutes when Woolford's left-foot drive whistled over the bar.
It took a brave piece of keeping by Forde to deny the dangerous Woolford when the Iron man threatened to get on the end of a low cross that skidded across the face of goal before Hayes saw his 29th-minute shot deflected over for Iron's only corner of the half.
But this Millwall are side are nothing if not resilient and having been on the back foot for spells of the opening half, they gradually worked their way back into it.
A neat piece of interplay between Grabban and Harris saw the latter's cross picked up by Dave Martin, but his shot was somehow scrambled clear.
However, the game was turned on its head in an amazing two-minute spell in which Jackett's side struck twice to stun Scunthorpe.
There seemed little danger when Gary Alexander picked up Zak Whitbread's header with his back to goal on 37 minutes. But The Lions' top scorer chested the ball down, swivelled and with one almighty swing of his right boot hit an unstoppable shot that gave Murphy no chance.
The decibel level amongst Millwall's travelling army of support reached breathtaking levels just 90 seconds later when Alexander's header from a Martin cross squirmed through Murphy's hands and over the line to hand Millwall a 2-1 advantage at the break.
Midfielder Abdou was repalced by Marc Laird at the start of the second-half in a like-for-like switch, with the Frenchman on the receiving end of a couple of rash tackles from Iron during the opening 45 minutes.
Scunthorpre made a change of their own 10 minutes after the restart with former Lion Liam Trotter replacing Togwell.
And Trotter, who had a spell on loan at The Den when Willie Donachie was manager, nearly came back to haunt his former club when, with virtually his first touch of the ball, he drilled an effort that Forde brilliantly blocked before Harris headed the loose ball clear.
Chris Hackett was introduced to the fray just past the hour-mark.
But it was The Lions who were made to feel hot under the collar when Sparrow kept his cool to fire home a 70th-minute leveller from close range as the balance of this absorbing encounter swung back Scunthorpe's way.
Back came Millwall, and Alexander was left cursing his luck after squandering a gilt-edged opportunity a couple of minutes later.
Harris played in Hackett on the right, his delicious delivery was on a plate for the unmarked Alexander, but he somehow powered his header wide with the goal at his mercy.
That proved to be a costly miss and with time ticking away, it was Scunthorpe who looked more comfortable in the energy-sapping heat.
And so it was that, with five minutes remaining, the ball ping-ponged in the Millwall area and there was Woolford to slam home under the body of Forde to put Iron in the driving seat.
On came Paul Robinson as The Lions tried to build up one last head of steam to score an equaliser that would take this titanic tussle into extra time.
Harris had a glorious chance to do just that when his low shot was diverted by Murphy at full stretch for Millwall's eighth and final corner of the game.
Despite one last roar of encouragement from three sides of the stadium, The Lions could not find that one penetrative pass or shot to level matters up for one last time.
The final whistle was met by disbelief, despair and many, many tears from both Millwall's players and fans as reality hit home - it's back to business in League One next season.
The progress that the club has made in the past 12 months is something solid to build on to ensure that we come back stronger than ever before.

Millwall: Forde, Dunne, Frampton (Robinson, 89mins), Bolder, Whitbread, Craig, Martin, Abdou (Laird, 46mins), Harris, Alexander, Grabban (Hackett, 62mins). Subs not used: Pidgeley, Barron.
Booking: Craig (83mins)
Scorer: Alexander (37, 39mins)

Scunthorpe United: Murphy, Byrne, Crosby, Mirfin, Morris, Sparrow, McCann, Togwell (Trotter, 55mins), Woolford, Hayes, Hooper ( Forte, 80mins). Subs not used: Lillis, Wright, Thompson.
Bookings: Togwell (9mins), Sparrow (16mins)
Scorers: Sparrow (6, 70mins), Woolford (85mins)

Ref: Michael Oliver
Att: 59,661