Arsenal's bid for a top-four finish suffered a major setback as Steve Morison's late goal earned Norwich a deserved point in a six-goal thriller at the Emirates.
Yossi Benayoun's opener in the second minute had seemed to put Arsene Wenger's side on course for an easy afternoon.
But with Norwich having gone ahead through Wes Hoolahan and Grant Holt, a double from Robin van Persie seemed to have won it for the hosts before substitute Morison stunned the home crowd with a smart finish five minutes from time.
Without a victory in their last three matches, Arsenal came flying out of the blocks and took the lead inside the opening 70 seconds.
Nothing seemed on when birthday boy Benayoun received the ball from Tomas Rosicky but he cut inside Kyle Naughton and curled a beauty beyond the reach of John Ruddy for his third Premier League goal of the season.
It was a dream start but Norwich have proved they are no pushovers this season and they immediately went in search of an equaliser.
Holt was unlucky to see his goalbound effort blocked by Kieran Gibbs in the sixth minute, with the visiting skipper then heading over from Simon Lappin's high cross.
Less than a minute later, however, Lambert's side did draw level as Naughton's low cross picked out Hoolahan and his firm side-footed shot somehow squirmed past an embarrassed Szczesny.
Van Persie had a golden opportunity to restore Arsenal's lead at the other end but fired over, while Holt was unlucky to be flagged offside from Simeon Jackson's clever through ball.
Norwich looked content to try and hit their opponents on the break and that tactic paid dividends in the 27th minute.
A quick break saw Hoolahan play in Holt and his shot took a lucky deflection to loop over Szczesny and into the net for his 16th goal of a wonderful season.
Van Persie was inches away of an immediate equaliser from Sagna's weighted cross but Arsenal then struggled to break down Norwich's rearguard effort.
Benayoun was lucky not to be shown a red card after lashing out at Bradley Johnson off the ball, while the visitors had two great shouts for penalties that were waved away by referee Anthony Taylor.
After leaving the pitch to a chorus of boos, Wenger's side made a slow start to the second period and should have been punished when Jackson was through on goal but the Canadian fluffed his lines.
Hoolahan also went close to extending Norwich's lead with a volley before the introduction of Alex Oxlade-Chamberlain gave Arsenal some much-needed extra impetus.
Van Persie had wasted two great opportunities to equalise but he made no mistake when Song's weighted ball into the box picked him out and he volleyed superbly into the corner of the net.
The Dutchman could have doubled his tally soon after, although there was a touch of fortune when he finally did in the 80th minute.
The ball deflected straight into the 28-year-old's path 12 yards out and he swept home past Ruddy to give Arsenal the lead.
Amazingly, though, Norwich weren't prepared to give up the ghost and a brilliant pass from Jonny Howson played in Morison to dispatch a perfect shot into the corner of the net.
Wenger's side were stunned but should have been awarded a penalty late on when Naughton appeared to nudge van Persie in the back, while the skipper and Song were both denied at the death by saves from Ruddy.