Ryan McCann released Peter McDonald beyond the home saints' back line with a clever lob and the visitors' top marksman cracked a low right-footed shot beyond the helpless Craig Hinchcliffe.
John O'Neil retaliated within a minute, his left-footed shot being finger-tipped aside by Craig Samson and trickeling along the goal-line and out of play just before David van Zanten could apply the finishing touch.
McCann hit a shot straight at hinchcliffe and O'neil volleyed a Kirk Broadfoot cross wide as both sides moved forward at every opertunity.
St Mirren equalised 5 minutes after the interval; Hugh Murray's corner was glanced home from 8 yards by the long right-leg of Broadfoot.
Hinchcliffe excelled himself with a flying save from a McDonald free kick and Broadfoot charged forward again to fire a low-drive inches wide.
The home keeper made another fine save to deny Sean Webb, who's header from Kieran McAnespie's cross was creeping in only for Hinchcliffe to dive low to his right to palm the ball behind.
The game was petering out in the second minute of stoppage time when Andy Millen was injured by McDonald who's shocking tackle merrited an immediate red card from referee Hugh Dallas.
When Millen recovered from the blow to his lower abdoman, he had to be restrained from following McDonald up the tunnel to exact retrebution.