High-flying West Ham may have aspirations of making it to the Premiership.
But they were well and truly grounded by the Seagulls as Guy Butters swooped to steal the unlikely winner that left the Eastenders in an unsightly mess.
Unchanged following last week's 2-1 win over Queens Park Rangers, West Ham quickly set about lowly Brighton who had lost 3-1 at home to Crewe Alexandra.
As early as the third minute, top scorer Marlon Harewood struck the left post with a fierce, low 18-yarder and that set the tone for a totally one-sided game.
Albion, sitting precariously in 21st place, handed a debut to Steve Claridge who had moved along the south coast from Weymouth, and although the striker soon outwitted fellow veteran warhorse Chris Powell, no one was there to capitalise when he swept a low centre across the six-yard box.
But while the hungry Claridge toiled tirelessly for the few scraps that came his way, the Hammers forward line could have had a goal feast with the chances that fell to them.
However, a combination of wayward shooting and lackadaisical finishing saw Harewood, Don Hutchison, Luke Chadwick and Carl Fletcher each fail to seize their moment as the first half somehow ended goalless.
Michel Kuipers had enjoyed a charmed life in that opening period and, on 50 minutes, the Seagulls keeper bravely clawed out Matthew Etherington's angled shot a split-second before the pair collided heavily.
That spelt the end for the Hammers' wide boy who hobbled away to be replaced by Bobby Zamora – a player who scored 76 goals in 125 league appearances for Albion before his transfer to Tottenham Hotspur in summer 2003.
Alan Pardew also introduced Nigel Reo-Coker in the hope that the double substitution might prove the catalyst for a long-overdue goal and after Harewood slid the England Under-21 midfielder's low cross into the side-netting the breakthrough did, indeed, finally come.
But to the amazement of the entire East End and the 29,514 Upton Park crowd, it was Brighton who broke the deadlock on 68 minutes when Butters headed home Richard Carpenter's deep, hanging cross after Tomas Repka needlessly conceded a free-kick.
The frustration was too much for West Ham to bear and when Adam Virgo recklessly scythed through Hayden Mullins just a few minutes later, neither player was going to escape an inevitable red card following the unsightly melee that ensued.
Still ten-man West Ham continued to press.
And still ten-man Brighton – who failed to win a single corner during the entire 90 minutes - continued to soak up the pressure all the way through to a final whistle that signalled three points and elevation to 18th place.