Darlington grabbed their first win of the season thanks to two goals in the last ten minutes which brought relief to supporters in the new Reynolds Arena.
Darlington had dominated the opening 45 minutes but the Leyton Orient goal remained intact at the interval.
The home side had gone close in the sixth minute when striker Glen Robson rounded keeper Glen Morris and then saw his goalbound effort cleared off the line by Greg Heald.
A minute later Orient midfield Billy Jones had two chances to score. Firstly he mis kicked and then with his second attempt he ballooned the ball over the crossbar.
Darlington hit back and defender Ryan Valentine fired narrowly wide and then midfielder Chris Hughes sent an inswinging corner under the crossbar, which Morris had to punch over the bar.
Valentine then hit a post in the 22nd minute and the same player crossed for Barry Conlon who glanced a header wide seven minutes later.
The visitors finished the half stronger and in the 40th minute Matthew Brazier fired over the bar and then a minute later Tom Newey fired wide.
Orient began the second half brightly and Jones was unfortunate to send his header into the arms of Darlington keeper Andy Collett in the 55th minute.
But the visitors quickly took the lead through striker Lee Thorpe. Thorpe acrobatically beat Collett from 12 yards with a reverse overhead kick.
The game became disjointed and there was a flurry of bookings from Hull referee Carl Boytson.
But Darlington kept their discipline and were rewarded with an equaliser in the 80th minute.
Makeshift attacker Matthew Clarke headed in a Chris Hughes corner and then a minute from time the roles were reversed when Clarke centred and Hughes volleyed in the winner to send the home crowd wild.
After the game Darlington boss Mick Tait said of goalscorer Hughes: "He has been bright and breezy in training and deserved his start.
"He creates chances for others and as he showed at the end can also put the ball away himself." Disappointed Orient manager Paul Brush said: "We scored a good goal which Lee does in training all the time.
"We didn't play as fluently as we can and although we didn't want to sit on our lead we were probably guilty of being too adventurous."