FULL-TIME: Scunthorpe United 1 Crystal Palace 2
The midfielder curled home an excellent left-footed shot past the despairing dive of home keeper Joe Murphy from the edge of the box in the closing stages of stoppage time - just when it looked like Scunthorpe had done enough to earn to earn a draw.
Behind to Darren Ambrose's angled drive in the 64th minute, David Mirfin looped home a header from a Michael O'Connor corner six minutes from time to get the Iron back on level terms.
It was a goal that had completed a stunning comeback from the home side, who had been reduced to 10 men when Marcus Williams was sent off for a professonal foul in the 72nd minute, but counted for nothing when Danns later struck.
Nigel Adkins had made just one change to the Scunthorpe side that won 1-0 at QPR for the visit of another London club.
On-loan Manchester City winger Donal McDermott came in on the left wing in place of Martyn Woolford to make his first start for the club.
Both teams started brightly, with McDermott twice off target and Grant McCann flicking the ball over the top as he met an inswinging cross with his right foot.
Garry Thompson also went close, doing excellently to keep a ball in on the right touchline before racing inside and firing in a low shot that was well held by Palace keeper Julian Speroni.
The best chance of the half though fell to Iron skipper Cliff Byrne, who spurned a golden chance to put the hosts in front in the 14th minute.
A McCann corner bounced around the box and landed at the Irishman's feet with the goal gaping, but somehow the full-back scuffed his shot a few yards wide of the target, to the disbelief of everyone at Glanford Park.
Scunthorpe continued to dominate the first half, winning an incredible nine corners, but could not break the deadlock before the break.
Four minutes after the interval, they again went close.
Gary Hooper streaked clear to pick up a long clearance from David Mirfin, but pulled his low cross just behind strike partner Paul Hayes with the goal at United's mercy.
It was an effort which pretty much summed up Scunthorpe's attacking threat.
Suddenly, Palace seemed to grow into the game, with Ambrose flashing a shot across the face of goal via the aid of Joe Murphy's fingertips.
The Eagles front man went over to the left to take the resulting corner himself and, when the ball was cleared back to him out wide, the former Newcastle and Charlton man had an acre of time and space to drive into the box before slamming home a great low effort through a crowded box.
Things turned from bad to worse for United in the 72nd minute, when Williams clumsily felled Palace sub Kieron Djilali as he raced through on goal.
It was a challenge that brought an immediate red card from referee Paul Tierney, despite the fact that defensive duo Rob Jones and David Mirfin looked to be covering in the box.
Just when it seemed the game had turned in the visitors' favour, Mirfin popped up with a great header to equalise for United.
It was a goal that should have secured Scunthorpe another valuable point, only for Danns to strike with only 60 seconds of added time remaining to complete a smash and grab raid for Palace.
TEAMS
SCUNTHORPE: Murphy; Byrne (C), Jones, Mirfin, Williams; Thompson (Forte 80), Togwell (O'Connor 83), McCann, McDermott (Moloney 78); Hayes, Hooper. Subs not used: Lillis (GK), Raynes, J Wright, Woolford.
PALACE: Speroni; Clyne, David, Lawrence (Hills 74), Hill; Carle, Derry (C), Danns; Butterfield (Djilali 64), Lee (Andrew 74), Ambrose. Subs not used: N'Diaye, Scannell, Comley, John.
Comment on this story