Celtic's hectic season looked to have finally caught up with them when Mark De Vries put Hearts two ahead with just 12 minutes remaining. Yet this Celtic side never know when they are beaten and goals from Chris Sutton and Didier Agathe gained them a share of the points from an incredible match.
Celtic's unbeaten 75-match home record would definitely have ended if De Vries had not managed to miss an open goal. When Paul Hartley teed up the chance the visitors were already a goal ahead, but unbelievably the Dutch striker completely miscued his shot from only six yards.
In the first half, Hearts were first to threaten when Neil MacFarlane, after playing a clever one-two with Robbie Neilson, threaded a pass between Bobo Balde and Stanislav Varga for Graham Weir to run on to, but unfortunately for the visitors the diminutive striker pulled his shot wide.
Hearts' slick passing was causing consternation in the home defence as the visitors forced two early corners. However, Celtic finally advanced on the Hearts goal after ten minutes but Alan Thompson's cross to Henrik Larsson was cut out by Scott Severin in the nick of time.
From a long ball by Jackie McNamara, Agathe's controlled the pass well and only a superbly timed tackle by Steven Pressley on the edge of the box denied the Celtic winger.
Stephen Pearson was dispossessed at the last minute by Alan Maybury in a swift Celtic counter-attack before Larsson's cross flashed across the face of goal, but beyond the reach of Sutton and Agathe.
In the 21st minute Hearts made the breakthrough their outfield play deserved. Hartley's drive deflected off Varga to Kevin McKenna who drilled a first-time left foot shot low past the helpless David Marshall in the Celtic goal.
Jambos keeper Craig Gordon then made a superb save from Agathe after he had flapped at a Stephen McManus cross, before Paul Lambert saw a 20-yard shot drift narrowly wide.
Larsson surprisingly lost control at the edge of the box but was alert enough to win a foul from Maybury, but Thompson's in-swinging free-kick was headed narrowly over by Varga.
McKenna nearly snatched another goal for Hearts just before half-time when he volleyed Gordon's long clearance, but Marshall managed to scramble the ball around the post.
The Bhoys powered forward immediately from the restart and Agathe sent over a dangerous cross that just eluded Larson.
Hearts were still a threat on the break though and from MacFarlane's clever pass, Neil Janczyk's shot from an acute angle was blocked by Marshall.
There were then loud appeals for a penalty when Pressley appeared to climb over Varga in the box, but referee Dougie McDonald was strong enough to resist the claims of most of the 59,348 crowd.
Then came a flair-up between McNamara and McKenna on the halfway line, which resulted in both players being shown the yellow card as the game turned nasty.
Balde missed a great chance to equalise when he was left unmarked at the back post from a Thompson corner but somehow headed over from only four yards. Sutton shot wide from Agathe's cross as a combination of slack Celtic finishing and Hearts defenders throwing themselves at every shot prevented the home side from troubling Gordon.
At this stage, Celtic manager Martin O'Neill sent on Stilian Petrov and Liam Miller, such was his concern that the match was slipping away. Miller was inches wide with a drive from a Larsson lay off, before the Celtic striker, who had a rare off day, scooped his shot over from Sutton's cut back.
Celtic's proud unbeaten home record looked dead and buried when Hearts went two ahead. From Neilson's long throw-in the ball broke to Hartley whose pass found De Vries and the striker showed quick feet in dispatching his shot low past Marshall.
But with just two minutes of normal time remaining, Miller's astute pass to Sutton allowed the former England striker to advance on Gordon and, though the Hearts keeper managed to parry his first effort, he was helpless in preventing the rebound flying high into the net.
This goal sent the home crowd into a frenzy after some had started to drift towards the exits, before a Larsson header was cleared off the line by Neilson from Thompson's flick.
After De Vries' glaring miss, Celtic incredibly drew level. Lambert's cross was headed on by Varga to Agathe who swept his left foot shot high in to the net from six yards to spark off amazing scenes of celebration.
There was still time for Maybury to send in a 20-yard shot which flashed just past the post before referee McDonald finally brought an incredible match to an end after almost five minutes of injury time.
Afterwards, a drained looking O'Neill claimed: "This was great entertainment and we showed incredible determination.
"We were two down with just a few minutes to go and the players could have easily have said that was it and preserved themselves for the Villarreal game on Thursday. I've commented before on our spirit and we pulled something from somewhere to get a result which was totally merited.
"We were off the pace in the first half - it may have been a hangover from the midweek John Kennedy incident - but it was a virtual onslaught in the second half. I thought if we got one we might get another, though Didier Agathe was a unlikely source." Disappointed Jambos boss Craig Levein added: "Even when we were two ahead I never thought the game was won as Celtic don't have that record without battling right until the end." Man of the Match: Jackie McNamara Though he was booked in an incident with Kevin McKenna, Celtic's Jackie McNamara embodied the never say die spirit which enabled Celtic to claw back a two-goal deficit in the last five minutes.