An early second-half goal by Pedro Moutinho saw Falkirk go 11points clear at the top of the table.
Falkirk looked dangerous from the start and Craig Hinchcliffe had to dart from his line to deny Darryl Duffy, who had profited from a move involving several team-mates.
Neil Scally, highly impressive throughout, fired in a drive after Duffy's energetic incursion into Saints' rearguard and Hinchcliffe was beaten but an outstretched foot diverted the ball for a corner.
Saints weathered Falkirk's early assaults and, led by Kirk Broadfoot, took the game to the visitors. A burst forward by the tall defender led to a Laurie Ellis cross which was cleared by Russell Latapy, who was everywhere for the league leaders.
Duffy had a drive held by Hinchcliffe and Mark Reilly replied with a volley which dipped over after Ellis's corner was headed out.
Saints' fans groaned when Brian McGinty mis-hit his cross after Mixu Paatelainen and Ellis had combined superbly down the left flank.
Ten minutes after the interval Moutinho collected a ball played down the inside-left channel and, although faced by four defenders, managed to swivel past them to release his shot. Hinchcliffe should have saved but allowed it to slip through his hands into the net.
Appallingly, Bairns' striker, Daniel McBreen, appeared to stoop down at the stricken 'keeper and jeer at his misfortune.
Falkirk sat back and new Saints' striker, Stewart Kean came close twice, hitting the side netting then shooting just wide, but Allan Ferguson in the away goal salvaged a point with an impressive save from a Broadfoot header.