Thomas Reilly's injury-time leveller handed St Mirren a share of the points in a 1-1 draw against Motherwell at Fir Park.
St Mirren were rewarded for spells of dominance by a last-gasp goal.
Micheal Higdon took advantage of some poor defending by Lee Mair and slotted beyond Craig Samson in the opening minute. St Mirren pressed for an equaliser throughout the remainder of the match and Shaun Hutchinson was dismissed in the closing stages.
However, in the last minute of injury time, Steven Thompson forced an excellent save from Darren Randolph before substitute Reilly bundled the ball into the net.
Hearts missed out on the chance to go top of the league as they were held to a 0-0 draw against Aberdeen at Pittodrie.
The Dons enjoyed the better of the chances against a Hearts side that looked jaded after their midweek exertions against Liverpool in the Europa League, although the Tynecastle men remain unbeaten in the SPL this season.
Despite their pressure, the hosts were unable to find a way past Hearts stopper Jamie MacDonald and were forced to settle for a second successive goalless draw at home.