Steve Morison struck a dramatic last-gasp goal as Millwall breathed fresh life into their promotion push with victory in a pulsating five-goal thriller at The Den.
Striker Morison kept his nerve in the third minute of injury-time to toe-poke the ball past Willy Gueret and spark wild celebrations amongst the home fans.
The game looked to be heading for a draw after former Lions striker Jermaine Easter hit a second-half brace on 46 and 79 minutes to cancel out earlier efforts from Andy Frampton (11mins) and Chris Hackett (20mins).
But cometh the moment, cometh the man in the shape of Morison, who finally got the reward his patience, perseverance and performance deserved to settle this match at the death.
Millwall had appeared to be in cruise control with an outstanding first-half display.
Boss Kenny Jackett tinkered with his team selection and formation, bringing in Danny Schofield for Jason Price and changing to a 4-5-1 system, enabling Dave Martin and Hackett to push on and support Morison in a lone striking role.
The tactical switch worked to perfection as The Lions got on the front foot from the start against their Play-Off rivals.
Considering the huge physical presence of Paul Ince's MK Dons outfit, the visitors looked suspect at set-pieces and struggled to cope with the slick, quick attacking football served up by Jackett's impressive Lions in the opening half.
Hackett, back to his best with a string of delicious deliveries from the right flank, had already twice tested keeper Willy Gueret from corners in the opening 10 minutes before finally providing a telling cross on 11 minutes that Frampton headed home with aplomb.
Hackett went from goal-maker to goal-taker nine minutes later. Schofield's effort following a quickly taken free-kick was blocked by Gueret, but Martin pounced on the loose ball and returned it for Hackett who doubled Millwall's tally with a crisp finish from 12 yards.
Former Den favourite Gueret did superbly well to deny the marauding Morison, flinging himself across goal to somehow claw the frontman's fierce drive away for yet another corner.
Skipper Paul Robinson also went close five minutes before the break with a firm header from Hackett's deep free-kick that flashed narrowly wide of the post.
Visiting boss Ince introduced Aaron Wilbraham for Luke Chadwick at the start of the second-half - and within 17 seconds of the restart The Dons had grabbed themselves a lifeline.
Striker Easter, who had a spell on loan at The Den last season, outpaced Frampton and Darren Ward and then thumped a 20-yarder that gave David Forde no chance.
MK could have added a second goal just 60 seconds later, but thankfully keeper Forde managed to smuggle Sam Baldock's shot away for a corner.
Forde came to the rescue again on 59 minutes with a forceful punch to clear Jason Puncheon's dangerous corner as the visitors continued to threaten.
Martin Devaney nearly capitalised on some hesitancy in the home defence, but thankfully the increasingly busy Forde was equal to his effort.
Lions boss Jackett introduced Adam Bolder to the fray in place of Marc Laird (69mins), with Lewis Grabban on for Martin (74mins) in a bid to provide additional cover to the back line and fresh impetus up front respectively.
Sandwiched in between the two changes came Millwall's first real attempt on goal of the half - a drive from Morison that was again diverted for a corner by Gueret.
But it was the visitors who continued to offer a greater goal threat and it was no real surprise when their second-half pressure paid off 11 minutes from time.
Easter was given too much time and space in the danger zone and took full advantage by rifling home with keeper Forde stranded to even things up.
The match really opened up now with The Lions finally showing the attacking zip and zest that had served them so well in the first half.
Millwall had a great chance to take the lead on 83 minutes when Bolder's hooked pass sent Grabban free. The offside flag stayed down and with Morison perfectly placed in the middle, Grabban unfortunately opted to blast rather than place his pass and hit the ball so hard it went out for a throw.
Within seconds it was The Lions goal that led a charmed life when Puncheon's cross fizzed across the face of goal and inches wide.
But Morison, who has been absolutely desperate for a goal, came up trumps with a sublime 93rd-minute finish, converting possibly his hardest chance of the night.
And despite nearly six minutes of injury-time being played - two minutes more than the four that were actually shown - Millwall, and Morison in particular, were not going to let that precious lead slip away once more.
Millwall: Forde, Dunne, Frampton, Abdou, Robinson, Ward, Schofield, Laird (Bolder, 69mins), Martin (Grabban, 74mins), Morison, Hackett (Fuseini, 90+3mins). Subs not used: Sullivan, Grimes, Smith, Fuseini, Price.
Scorers: Frampton (11mins), Hackett (20mins), Morison (90+2mins)
MK Dons: Gueret, Woodards (Howell, 51mins), McCracken, Powell, Lewington, Devaney (Leven, 74mins), Quashie, Chadwick (Wilbraham, 46mins) Puncheon, Baldock, Easter. Subs not used: Searle, Carrington, Gleeson, Morgan.
Bookings: Quashie (40mins), Puncheon (48mins), Easter (61mins)
Scorer: Easter (46, 79mins)
Ref: Roger East