St Mirren's push for Europe suffered another setback after a heart-breaking injury time equaliser denied them a potentially crucial three points.
With the Buddies looking to return to European football for the first time since 1987 next season, it looked crucial for Stephen Robinson's side to pick up a win against European spot rivals Hearts in Paisley - especially after their defeat to Hibs the previous weekend.
And the Saints initially responded to the pressure superbly with an excellent first half performance. Captain Joe Shaughnessy produced a poacher's finish on his return to the starting line-up to break the deadlock, with fellow defender Ryan Strain doubling their lead with a sublime free-kick.
Hearts threatened to sneak their way back into the match after the break when Josh Ginnelly tapped home at the back post.
Peter Haring's red card looked to have put paid to the Jambos hopes of a comeback.
But Saints substitute Ryan Flynn's foul on Ginnelly gave Hearts the perfect chance to equalise at the death, with Lawrence Shankland slotting past Trevor Carson to see the points shared.
The Buddies' hopes of making it into Europe are undoubtedly now slimmer, with Robinson's men sitting three points behind Hibs and four behind the Jambos with just three games left to play.
St Mirren skipper Shaughnessy came back into the heart of the defence for the crucial clash, with Richard Taylor also introduced at the expense of Charles Dunne and Declan Gallagher.
Greg Kiltie continued to deputise in place of Keanu Baccus, with Alex Greive keeping his place up front.
Both sides went into the game desperate for a win to boost their respective European hopes, and it was the away side who started more brightly in the Paisley sunshine without creating any clear cut chances.
Andy Halliday was fortunate to avoid a booking after nine minutes after crashing into Kiltie on the left wing, with referee David Dickinson keeping his cards in his pocket.
Saints supporters were screaming for a penalty when a cross into the box appeared to hit Hearts defender James Hill's hand. Again the appeals fell on deaf ears.
Kye Rowles did eventually go into the book for cynically pulling down Greive in an increasingly hot-tempered clash, with Dickinson's decision greeted by ironic cheers from the home support.
Ryan Strain was first to test Hearts keeper Zander Clark's reflexes, fizzing a low strike from the edge of the box that was well held by the keeper.
Shaughnessy did well to cut out a dangerous Josh Ginnelly cross after the Jambos winger skipped past Marcus Fraser, with Hearts looking the more likely to trouble the scoresheet in the opening stages.
Taylor joined Rowles in the referee's book for a blatant foul on Yutaro Oda after the speedy forward had already skipped past Alex Gogic.
Hearts defender Sibbick produced a crucial block to deny Greive's low effort after the New Zealand international scampered through on goal.
St Mirren thought they'd opened the scoring on the 26 minute mark when Alex Gogic tapped in from close range, but the linesman's flag denied the hosts an opener.
The cards were flying in Paisley, with Strain next in the book after pulling Barrie McKay as he burst towards goal.
With ten minutes left of the first half St Mirren crucially got their noses in front. Scott Tanser's corner to the back post was headed back into the danger zone by Alex Gogic, with skipper Shaughnessy lurking in the six-yard box to ghost past Hearts static defence and poke past Clark.
Main had a gilt-edged chance to double the home side's advantage just before the break. Grieve did brilliantly on the break to keep an attack alive, threading his strike partner in but Clark produced a fine one-handed stop to deny the forward.
On the stroke of half-time the Buddies did double their lead in emphatic style. Mark O'Hara won a free-kick 25 yards out after James Hill went into the back of the midfielder. Strain stepped up and fired straight into the bottom left corner past Clark to put the Saints in an even stronger position at the break.
Dunne replaced Taylor at the start of the second half as the Buddies looked to carry forward their positive momentum.
The centre back was straight into the action, recovering after an initial mistake to halt Lawrence Shankland's run into the box.
Australia international Baccus replaced Greive, who was struggling with a knock, with just over half an hour on the clock as the Saints looked to strengthen their hold on the match.
The Saints had the wind in their sails and almost went three ahead when Strain skipped inside after a corner was cleared to him on the edge of the box. His curling effort drew a brilliant save from Clark.
The away side's support hadn't had much to cheer about but Hearts started their comeback when Ginnelly tapped home Nathaniel Atkinson's cross at the back post to halve the deficit with 18 minutes left on the clock.
The hosts chances of holding on to all three points were given a huge boost when Peter Haring was given a straight red card for scything down O'Hara as the midfielder burst away down the left wing.
Saints sub Thierry Small almost made it three when he latched on to a Lewis Jamieson pass, with Clark denying the defender at the near post.
And that miss proved to be costly when Ryan Flynn clumsily brought down Ginnelly inside the box deep into injury-time.
The foul allowed Shankland the chance to level with the last kick of the ball, with the Scotland international sending Trevor Carson the wrong way from the spot to sneak Hearts a point.
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