Mansfield defender Rhys Day went from villain to hero to put a huge dent in Darlington's play-offs hopes.
Day, who had seen his first minute penalty save, headed in an Adam Rundle cross two minutes into injury time to deny Darlington a vital victory.
Veteran striker Clyde Wijnhard looked to have clinched the stuttering Quakers second win in five games in the 66th minute but never say die Mansfield had the final say. The Stags had given a full league debut to 21-year-old keeper Jason White after four years on the bench.
But it was White's opposite number Sam Russell who was first into the action when he saved Day's early penalty after just 25 seconds. Neil Wainwright fouled Rundle but Day's weak spot kick was comfortably saved by the diving keeper.
Ironically seven days earlier Day had converted his first ever Mansfield penalty a few minutes after team-mate Richie Barker missed his penalty in the 5-2 defeat against league leaders Yeovil.
White finally touched the ball in the ninth minute holding on to a couple of dangerous Wainwright crosses before Joseph Kendrick fired over from 20 yards at a well worked free-kick.
Midway through the first half Alun Armstrong deflected another dangerous Wainwright cross narrowly over as Darlington gained the upper hand then white made his first crucial save, clinging on to Steven Thomas' close-range drive.
In the final five minutes of the half, Simon Brown and Rundle had goal-bound shots blocked as Mansfield fought back.
Six minutes into the second half, Rundle was again denied this time by Russell's acrobatic stop.
But in the 66th minute Darlington, who always looked threatening on the break grabbed the lead.
Debutant Matthew Bates picked out Wainwright with a fine curling pass and the winger raced clear before crossing for the unmarked Wijnhard to tap in.
Four minutes later Russell also gifted Mansfield with an equaliser but the keeper redeemed himself for a poor clearance to tip away Barker's fierce closer-range shot.
14 minutes from time debutant White kicked away Wijnhard's poweful 10 yard finish and that fine save proved vital when Day struck two minutes into injury time.