St. Mirren 1 Falkirk 5
Two goals up within the opening 15 minutes, they withstood a brief St Mirren fightback before another lethal flurry in the closing ten minutes.
The warning signs were already there by the time Portuguese Pedro Moutinho grabbed his and Falkirk's first goal.
Barely two minutes after Graham Barrett fired a half-volley fractionally over, Moutinho burst into the penalty box through a series of powder-puff tackles before toe-poking the ball past goalkeeper Chris Smith.
Steve Thomson's sweetly struck effort from the edge of the area soon doubled Falkirk's advantage and only poor finishing from Craig Higdon, when he was completely unmarked, denied the visitors a 3-0 lead inside the opening quarter of an hour.
St Mirren's best two contributions to the first half both came in a 60-second spell with on-loan midfielder Chris Birchall sending a free header over and Billy Mehmet then forcing an excellent save from Tim Krul.
But Falkirk were soon back on top and Thomson somehow scooped a shot high into the air when it seemed easier to score.
Barrett then wasted another clear chance but Falkirk eventually got the third goal that they deserved five minutes before the break when Moutinho clipped an angled half-volley into the top corner of the net.
Saints needed to pull a goal back and did so early in the second period with Birchall crossing for Mehmet to hammer home at the near post.
Franco Miranda almost made things very interesting in the 64th minute, but his looping long range free-kick came back off the bar with Krul beaten.
That deflated the home side and it was little surprise to see Barrett put the game beyond them with a late diving header from Moutinho's cross.
St Mirren's misery was completed five minutes from time when substitute Carl Finnigan picked up a long clearance, skipped past keeper Smith and found the empty net.