The home side had weathered some early United pressure when they took the lead in the 14th minute. Darlington midfielder Jonjo Dickman struck an upright with a low drive and when the ball bounced out Tresor Kandol was on hand to tap the ball in from close range.
Torquay grabbed a late first half equaliser after ending the half with a flurry. A long throw from captain James Sharp beat the Darlington defence and Martin Phillips fired in from 12 yards out just seconds before the interval.
Early in the second half United had chances to take the lead. In the 48th minute Steve Woods fired inches wide and then two minutes later Jo Kuffour brought a fine save from David Knight.
Darlington should have taken the lead in the 60th minute but they were denied a clear penalty after Alex Lawless had handled inside the area.
However Darlington did take the lead in the 76th minute when Clarke Keltie put Guylain Ndumbu-Nsungu in the clear and the big striker raced forward before lashing the ball past Andy Marriott in the Torquay goal.
Towards the end Ndumbu-Nsungu had opportunities to seal the game but he failed to take them and when Torquay substitute Alan Connell grabbed a last minute equaliser it looked as though Darlington had thrown away the chance of a victory.
But the game had one last twist and in time added on Keltie was brought down by Sako and Ndumbu-Nsungu sent Marriott the wrong way from the spot.
Sako was booked for his protests and he continued the argument before the game could restart and received a second yellow card and was sent from the field closely followed by manager Rosenior.