Jermaine Jenas stole in before the break to take full advantage of Michael Dawson's nod-down from a Michael Carrick free-kick after Michael Essien shot his side into an early lead. The home side had plenty of possession and applied pressure in the second half, but the boys looked like seeing it out until Gallas' late intervention that left the team stunned at the final whistle - unable to believe another late blow.
Martin named an unchanged side on an afternoon when Chelsea marked the passing of Peter Osgood with a number of his former teammates on the pitch including Terry Venables and George Graham.
Hernan Crespo pinged the ball across the face of goal in just the second minute, with Joe Cole not too far away from making a connection, before Jermaine Jenas was forced into an in front of goal clearance to keep the match goalless.
The boys didn't seem to be having problems picking out space in Chelsea's defensive third, Teemu Tainio found Mido on seven minutes and the big striker smashed the ball across goal - leading to a little spell of pressure.
Moments later though, Shaun Wright-Phillips got the better of Tainio and tested Paul Robinson to his near post. The ball ran loose making a clear-cut opening for Essien and was thankfully spooned wide by the ex-Lyon man.
On 13 minutes the home side did make the breakthrough when the team were overplaying a bit in front of their own goal and Michael Carrick, of all people, misplaced his pass across the area, which was seized on by Wright-Phillips down the right flank. The little winger squared for Essien and this time the midfielder made no mistake and registered his first goal for Chelsea.
Robert Huth tried his luck from all of 25 yards on 24 minutes and his swirling effort bounced off the chest of Robinson before being shepherded to safety. The attacking theat was there from our team, but you suspected they were guilty of one pass too many on approach.
The game then meandered towards half-time with neither side looking particularly likely to trouble the scorers until Joe Cole livened up proceedings from a home point of view with an effort that zipped across the face of Robbo's goal.
A minute before the break and it was us recording a goal - taking advantage of Chelsea's failure to go for the jugular when in front. A foul on Lee Young-Pyo led to a free-kick down the left flank, which was duly taken by Carrick. His flighted ball into the area was met by a mighty leap and downward header from Dawson and it was Jenas who pounced on the ball to stab past Cech for his sixth goal of the season.
Cole tested Robbo's reflexes when the second half got underway, with Robbie Keane posing a little test for Petr Cech at the other end with a chip towards the top corner. Gallas then ventured down the right and drove in a swirling effort that was clutched high by Robinson at the second attempt.
The pressure was building and a low cross from Crespo was intercepted by Ledley King, but the ball spun off his boot and landed on the roof of the net. From the resulting corner John Terry forced a fingertip save from Robinson with a powerful header.
Jose Mourinho opted for double change on 68 minutes, introducing Damien Duff and Didier Drogba to the mix in place of Wright-Phillips and Cole. A dramatic moment followed six minutes later when Dawson headed back to Robinson but reckoned without Crespo chasing the ball down. The England goalkeeper was forced to lob the ball over the head of the striker before clattering into Duff in order to finally make his clearance.
On 78 minutes it was Jenas who could have added to his tally after accepting a driving ball from King and brilliantly darting past Gallas. Unfortunately his shot on goal was a bit too comfortably gathered by Cech.
There were a couple more scares in the closing minutes - particularly Drogba smashing against the post - but heartbreak was to follow in added time when Stalteri cleared the ball only as far as Gallas and the Frenchman strode forward and curled the ball past a despairing Robinson to reap the points for Chelsea.
A William Gallas strike in stoppage time denied us what looked a likely point in a dramatic finish at Stamford Bridge.