Murray Wallace was the hero once more as the defender's early header won Saturday afternoon's Emirates FA Cup Fifth Round tie at AFC Wimbledon 1-0.
The defender popped up to head home Ryan Leonard's cross just five minutes in to send Millwall into the Quarter-Finals of the competition once more.
Neil Harris made one change from Tuesday night's goalless draw with Sheffield Wednesday, as Alex Pearce started in place of Shaun Hutchinson, who dropped to the bench - a place that was also occupied by Tom Elliott, who returned from injury and illness.
The hosts started the brighter and nearly took the lead with just two minutes played, but Joe Pigott's shot struck the post with Jordan Archer an onlooker.
However, three minutes later it was The Lions who got their noses in front, as Murray Wallace arrived unmarked to powerfully head home Ryan Leonard's cross.
A scrappy period was to follow, until around the midway point of the half when Michael Folivi broke forward, but he shot wide. Anthony Hartigan then tried his luck from distance, but the effort was blocked. The home side kept coming and fashioned another chance with 32 minutes on the clock, but captain Deji Oshilaja headed over from Toby Sibbick's cross.
Millwall's first real spell of possession came with 10 minutes to go until the half-time break, but it was to end with Jed Wallace blazing high, wide and not so handsome.
Wimbledon started the second half in determined mood, but could only muster an effort from Sibbick which found the roof of the stand behind the goal. With 55 minutes on the clock Lee Gregory shrugged off his marker and slotted in Aiden O'Brien, but the Irishman's poke at goal was saved by Aaron Ramsdale.
On the hour mark, Millwall were presented with a chance after Gregory knocked the ball down into the path of Jake Cooper, but his shot went wide. At the other end, Folivi struck towards goal, but Archer comfortably saved.
Murray Wallace's deep cross caused problems on 67 minutes, but as the ball fell to Cooper at the back post, he nodded wide. Three minutes later, the home support were on their feet as referee Jon Moss blew after a tackle inside the box, but the linesman had instead given offside.
Shaun Williams tested Ramsdale from range with 15 minutes remaining, whilst Gregory found himself in on goal just moments later, but Dons substitute Andy Barcham executed a perfect last-ditch tackle - Williams' follow-up was blocked by the goalkeeper.
Ryan Leonard and Gregory both had efforts as the clock began to tick towards the conclusion of the afternoon, with the former also letting fly from distance on 84 minutes, but it was deflected behind, with the following corner-kick coming to nothing.
Jed Wallace won possession in the midfield with 87 minutes on the clock and darted towards goal, but his final touch allowed Ramsdale to come out and smother. Substitute Dylan Connolly then got his effort horribly wrong at the other end.
Anthony Wordsworth had two attempts to equalise as the game reached its dying embers, but both failed to trouble Archer. Jed Wallace was then sent through as the match entered three minutes of stoppage-time, but Mitchell Pinnock raced back to tackle and send the ball behind for a corner.
The remaining seconds of injury-time were negotiated without too much trouble - Millwall are in the last eight once more!
AFC Wimbledon: Ramsdale, Oshilaja, Nightingale, Hartigan (Pinnock 63'), Garratt (Barcham 46'), Sibbick, McDonald, McLoughlin, Pigott (Connolly 63'), Wordsworth, Folivi. Subs not used: McDonnell, Thomas, Wagstaff, Soares.
Millwall: Archer, Cooper, Williams, J. Wallace, Gregory (Hutchinson 90+3'), Ferguson, Romeo, Pearce, O'Brien (Elliott 64'), M. Wallace, Leonard. Subs not used: Martin, Tunnicliffe, Morison, Skalak, Hanson.
Scorer: M. Wallace 5'
Booking: M. Wallace
Referee: Jonathan Moss