Didier Konan struck a stoppage-time winner to give Hannover a dramatic Europa League victory that just moments earlier looked to have been snatched away from them.
Hannover were on course for a win for much of the match thanks to Mame Diouf's early goal but hosts Helsingborg appeared to have snatched a point right at the death when substitute Alvaro Dos Santos equalised a minute into injury time.
However, there was still another twist in the tale as, with three of minutes of added time up, Konan fired in from close range to earn Hannover the points and keep them a point clear of Levante at the top of Group L.
Helsingborg, meanwhile, continue to prop up the standings with one point after their agonising loss.
Hannover had already gone close a couple of times before taking the lead, with Diouf firing over from close-range in the opening minute and Mohamed Abdellaoui unable to hit the target from 20 yards soon after.
There was no denying Diouf in the 12th minute as the former Manchester United man powerfully headed home Szabolcs Huszti's corner.
The German side looked likely to add to that lead as the game progressed with Diouf heading wide, Mario Eggiman seeing his header tipped over by Par Hansson, who also produced a fine save to push a Sergio Pinto shot round the post.
Helsingborg were not without a threat of their own though, and they came within inches of an equaliser in the 40th minute when Nikola Djurdjic's header from a corner struck the post.
Hansson was back in action in the 51st minute to turn behind a Huszti shot while at the other end Alvaro was soon making an impression after coming on as a 66th-minute replacement with a shot that was blocked by visiting keeper Ron-Robert Zieler.
Both sides continued to create openings in the closing stages, but none of them were taken and, when Alvaro missed from just a few yards out late on, the game looked to be Hannover's.
However, Brazilian Alvaro made amends for that miss when he levelled the scores up after rounding Zieler and slotting home.
That could have been heartbreaking for Hannover, but they showed great character and determination to go straight back on the attack and were rewarded when Konan slotted in a last-gasp winner.