Millwall crashed to a second defeat on the spin as they allowed Bournemouth to turn a 2-0 deficit into 5-2 victory with a stunning second-half show.
Martyn Waghorn (6mins) and Liam Trotter (10mins) handed The Lions a 2-0 lead, only for Ryan Fraser (43mins) to reduce the arrears just before the break.
Bournemouth then produced a sensational second-half show, drawing level on 49 minutes through Steve Cook before Harry Arter (55mins) fired the home side ahead from the edge of the area.
Alan Dunne was then shown a second yellow card for handball, leaving Millwall a goal - and man - down with over half an hour remaining.
Lewis Grabban duly despatched the spot-kick to put The Cherries 4-2 ahead, with another penalty - this time by sub Brett Pitman - completing the rout in injury-time.
Lions boss Steve Lomas rang the changes following the heavy midweek defeat at Birmingham City, bringing into Karleigh Osborne to partner Paul Robinson in the heart of defence, Shaun Derry for Nicky Bailey in midfield and Lee Martin for Steve Morison up front.
Little could Lomas, or the 1,375 travelling fans, quite believe how dramatic an impact those changes would make as The Lions roared into a 2-0 lead with just 10 minutes on the clock.
Former Den striker Grabban tested David Forde in the opening seconds with some neat work on the left flank and then whipped in cross that was held by the keeper.
However Millwall broke the deadlock after five minutes when Trotter's pass was picked up by Waghorn on the left, and he despatched a low angled drive beyond the reach of Stephen Henderson, one of two West Ham loanees making their Cherries debut.
The celebrations were still in full swing when Waghorn returned the favour, playing in Trotter, who despatched a delightful chip over the onrushing keeper and intop the back of the net.
It could have been 3-0 soon after as Waghorn broke clear of the home defence but failed to spot Martyn Woolford who had peeled away from his marker in space to his left. The striker went for goal himself and lashed well wide of the target.
Having established what looked to be a comfortable two-goal cushion, The Lions gradually took their foot off the gas as the half progressed - and The Cherries sensed a way back.
Tokelo Rantie twice fired inrto the side netting and only the brilliance of Forde - who somehow tipped over a rasping drive from Jack Collison - denied them a leveller by the 30-minute mark.
However there was little that Forde could do three minutes before the break when the visiting defence failed to really clear their lines and Fraser curled a low shot beyond the keeper's reach from 16 yards.
That goal gave Bournemouth a real belief that they could go on and claw their way back and the manner in which they ripped The Lions apart in the first 15 minutes after the break was to devastating affect.
Left-back Cook hauled the home team level on 50 minutes, powerfully heading home Ian Harte's corner and the latter was then a whisker away from scoring himself, only to see his sweetly struck free-kick smack the crossbar and bounce away to safety.
The Cherries then went ahead when the unmarked Arter lashed the ball past the stranded Forde to send the home side on their way to what had looked to be a most unlikely victory at one stage.
Millwall found themselves facing a second-half mountain to climb on 59 minutes when Dunne was shown a second yellow card for handling in the area, his second dismissal of the season, and Grabban duly sent Forde the wrong way from the penalty spot.
The shell-shocked Lions struggled to regain any of the composure or constructive play that had served them so well for the opening spell of the first half and it was very much a case of damage limitation for the remainder of the game.
There was still to be one further goal though, when Lions sub Paul Connolly was penalised for a foul and Cherries sub Pitman clinically converted into the bottom right corner to complete the rout.
AFC Bournemouth: Henderson, Francis, Cook, Ward, Harte, Fraser, Arter (Pitman, 86mins), Collison, Pugh (O’Kane, 83mins), Grabban, Rantie (Surman, 77mins). Subs not used: Jalal, Elphick, Hughes, Thomas.
Booking: Arter (61mins)
Scorers: Fraser (43mins), Cook (50mins), Arter (55mins), Grabban (pen, 59mins)
Millwall: Forde, Dunne, Robinson, Osborne, Malone, Abdou, Trotter (Morison, 58mins), Derry (Bailey, 58mins), Martin, Waghorn (Connolly, 61mins), Woolford. Subs not used: Bywater, Lowry, Bailey, Keogh, Easter.
Bookings: Dunne (13 mins), Malone (15 mins), Derry (20 mins)
Sending off: Dunne (59mins)
Scorers: Waghorn (6mins), Trotter (10mins)
Att: 9,624 (away 1,378)