Northampton came from behind to grab all three points in an absorbing encounter at the Reynolds Arena that brought Darlington's recent good run to an end.
The visitors fielded on-loan striker Magno Vieira and the Brazilian almost grabbed an early goal. Darlington keeper Michael Price denied the front man with a smart save in the opening 30 seconds of the game.
As the action continued, Darlington winger Neil Wainwright fired wide after two minutes and then soon afterwards a goal-bound shot from home striker Neil Teggart was deflected for the game's first corner.
Wainwright then cut inside from his position on the left flank and he curled a shot inches wide, in the ninth minute, as the home side stayed on top.
Teggart headed into the arms of Town keeper Lee Harper in the 13th minute and then six minutes later Darlington striker Barry Conlon thought he had made the breakthrough when heading in from close range. A linesman's raised flag cancelled out the effort for offside.
Vieira, after his bright start, was kept in check by Quakers defender Matthew Clarke but the Brazilian again found himself in space inside the area but he somehow fired wide from only six yards out in the 22nd minute.
Northampton broke out of defence in the 24th minute and Marc Richards fired into the sidenetting after being sent clear by Martin Smith.
The second half began with a bang as Darlington took the lead in the 47th minute. Harper attempted to clear his lines, but the ball hit defender Chris Willmott and bounced back into the net to give Darlington the lead.
The visitors brought on substitute Derek Asamoah in the 58th minute and his introduction turned the game in favour of Northampton.
The substitute saw a 71st minute effort cleared off the line by Darlington captain Craig Liddle and then three minutes later Asamoah earned his side a free-kick.
The ball was crossed into the Darlington area and defender Ian Clark hand-balled on the line to earn himself a red card and the visitors a penalty kick, which was dispatched by Smith into the bottom corner of the net.
Darlington were in disarray and down to ten men and the visitors took full advantage.
Chris Hargreaves crossed from the right and Richards volleyed in from five yards to give Northampton the victory that keeps alive their play-off hopes.