Full-time from The DenTen-man Millwall slipped to a third successive defeat and into the drop zone as Brighton made it five wins on the bounce to go top of the Championship table in a feisty Den encounter.
Goals from Ashley Barnes (17mins) and Adam El-Abd (50mins) put Gus Poyet's high-flyers into a commanding 2-0 position.
And when substitute Chris Taylor was sent off on 67 minutes for a second bookable offence, just 20 minutes after replacing Josh Wright, it looked to be game over for Kenny Jackett's side.
But spurred on by a home crowd clearly frustrated at what they felt to be the harsh dismissal of Taylor, The Lions dug deep and reduced the arrears when Chris Wood smashed home with 11 minutes remaining.
It took a superlative save by Seagulls stopper Tomasz Kuszczak to deny Wood his second goal deep into injury-time as Gus Poyet's side saw out a nervy finale to secure the three points.
"I was disappointed with the goals against us," said Kenny. "We gave ourselves a mountain to climb. As a side we've improved between the boxes but we're not getting it right in either box at the moment, particularly for the second goal." Lions boss Jackett had made two changes to the team beaten by Cardiff in midweek, replacing keeper Maik Taylor with David Forde for his first start of the season and bringing in loanee striker Wood for his full debut.
In a lively opening it was Wood who could have opened the scoring after four minutes when he met Scott Malone's cross but headed straight at Kuszczak.
Barely 60 seconds later it took a smart stop by Forde, diving low to his left, to avert the danger as Wayne Bridge's arrowed drive looked destined for the bottom corner.
Will Buckley then shot a fraction wide of the target as the visitors began to ask questions of the home defence.
It was no real surprise to see Brighton take the lead after 17 minutes, although the ease with which Buckley was able to progress down the right flank and cut-back for Barnes to drill home from 10 yards will have been a major disappointment to the manager.~
The Lions struggled to muster an instant response, and it wasn't until midway through the half that Malone's surging run and cross picked out Wood, who swept the ball over the bar from a tight angle.
It took a great defensive block by Shane Lowry to deny Buckley before James Henry first drew a sprawling save from Kuszczak and then saw his teasing delivery fumbled by the keeper, but Liam Trotter and Andy Keogh were unable to connect with the loose ball.
Jackett introduced Taylor for Josh Wright at the start of the second half and within 60 seconds of the restart - for the third game in a row, The Lions had a player booked.
On this occasion it was the sub who was shown a yellow card by referee Andre Marriner for a strong challenge on Inigo Calderon.
Brighton doubled their tally four minutes later when El-Abd rifled home after Millwall failed to clear Andrea Orlandi's corner.
It took a great clearance by Trotter to prevent Barnes' header from a Gary Dicker cross making it 3-0 before the game looked to be put out of The Lions' reach when Taylor was dismissed for a challenge on keeper Kuszczak, although minimal contact appeared to be made.
Down to 10 men and feeling a sense of injustice, The Lions finally kicked into gear and Wood ensured a grand-stand finish when he rifled home his first goal for the club from a tight angle.
The West Brom loanee so nearly grabbed a dramatic injury-time equaliser only for Kuszczak to made a crucial block.
Millwall: Forde, Dunne, Malone (Robinson, 62mins), Abdou, Lowry, Osborne, Trotter, Wright, Wood, Keogh (Henderson, 76mins), Henry. Subs not used: M.Taylor, Shittu, Batt, Smith.
Booking: C.Taylor (47mins)
Sending off: C.Taylor (67mins)
Scorer: Wood (79mins)
Brighton & HA: Kuszczak, Saltor (Calderon, 46mins), Greer, Hammond, El-Abd, Barnes, Orlandi (Lualua, 83mins), Mackail-Smith (Dicker, 42mins), Bridcutt, Bridge, Buckley. Subs not used: Dunk, Dobbie, Ankergren, Lopez.
Scorers: Barnes (17mins), El-Abd (50mins)
Ref: A. Marriner
Att: 12, 191 (Away 2,468)