Lee Gregory hit four goal as Millwall booked their place in the JPT Southern Area Semi-Final in an eight-goal thriller against League Two pace-setters Plymouth Argyle at Home Park.
The Lions took the lead with Gregory's fourth goal in eight games after 21 minutes but Jake Jervis levelled for the home side on 34 minutes, only for Gregory to restore Millwall's lead two minutes before the break.
Gregory was on hand to stab home his - and Millwall's third of the night - four minutes into the second-half to put Neil Harris' charges 3-1 up and within touching distance of victory.
In a pulsating encounter, Graham Carey's 55th-minute thunderbolt put Plymouth right back in it only for the home side to throw away their lifeline two minutes later, conceding a penalty that Gregory converted to grab his fourth and restore Millwall's two-goal cushion.
Aiden O'Brien made the game safe in the 66th-minute, finishing off a brilliant move involving Shaun Williams and Gregory, and although Jervis added his second of the night five minutes from time, The Lions' place in the Semi-Finals was secured.
Tuesday night's win was the first time since April 2001 that The Lions had scored five goals on their travels. On that occasion it was inspired by another hat-trick hero in the shape of Paul Ifill, who grabbed three goals in a 5-1 win at Cambridge United.
Lions boss Neil Harris, who was a key figure in that 2000/1 promotion-winning season, made four changes to his current Millwall team from the one that started against AFC Fylde on Saturday. Jordan Archer replaced David Forde in goal, Carlos Edwards returned at right-back, whilst George Saville and O'Brien slotted into midfield in a 4-4-2 formation.
The Pilgrims had failed to score in their previous three home matches against The Lions, and it took a couple of strong early interventions from Byron Webster and then Mark Beevers to break up promising moves from the home side.
After a fairly quiet opening the game suddenly sprung into action on 13 minutes when a Carey free-kick on the left was met by Argyle skipper Curtis Nelson, and his looping header smacked the top of the bar.
Millwall responded and a long throw by keeper Archer set O'Brien scampering away down the left, but his cross was cleared.
On 19 minutes Morison showed great persistence to win possession as two defenders dithered inside their own half and powered forward into the penalty area, only to be denied as he prepared to pull the trigger by a crucial tackle from Nelson.
However it took just two minutes for The Lions to make the breakthrough. Williams was the provider with a super cross from the left and Gregory finished the move off with a glancing header beyond the reach of keeper Luke McCormack.
Plymouth's response was positive - and immediate - with Jervis' shot on the turn well held by Archer.
The Lions then lost right-back Edwards to an injury on 33 minutes, and within seconds of replacement Sid Nelson entering the field, Plymouth were level. Gary Sawyer whipped in a ball from the left and Jervis, who was struggling to keep his balance, still managed to lash the ball high into the roof of the net from eight yards.
The home side's joy was short-lived and nine minutes later Millwall had restored their lead. Whilst not having anything like the power of Jervis' shot, a header by Beevers from Williams' corner took a deflection off Gregory and virtually drifted unnoticed into the bottom corner.
Harris' side had keeper Archer to thank for preserving Millwall's 2-1 lead as the teams went in at the break, brilliantly clawing away a header from Carl McHugh that was arrowing towards the bottom corner.
The Lions got the second-half off to a dream start and within four minutes Morison played in Gregory, and although the striker's first shot was saved, Gregory made no mistake by slamming home at the second attempt.
That two goal cushion didn't last long, however, and when Carey took aim from fully 35 yards after 56 minutes, there was nothing Archer could do other than watch the ball whistle past his outstretched hands and into the top corner.
It was now game on at 3-2 - again! - as far as The Pilgrims were concerned, yet they inexplicably handed Millwall an opportunity to score just two minutes after reducing the deficit. Gregory weaved his way into the penalty area, was hacked down and made no mistake with the resulting spot-kick to put The Lions 4-2 ahead.
On 66 minutes it was 5-2 to The Lions with O'Brien's sublime final touch a fitting end to a sweeping move in which Williams and Gregory combined to slice open the home defence.
Millwall had further chances to put this game way beyond Plymouth's reach, but Morison was twice denied by excellent saves from the home keeper as he honed in on goal.
It was Jervis who scored the last goal of the night with a crisp low finish on 85 minutes, but Lions captain Morison and his side had the final laugh, safe in the knowledge that this victory keeps Millwall on course for a fourth Wembley appearance in just seven years.