Dundee's Max Anderson saw red with 20 minutes remaining but – despite their numerical advantage – the Paisley side could not find a winner.
The Dark Blues had the first opportunity of the game with just seconds on the clock as Anderson swung a cross in from the right but Paul McGowan's shot was half blocked and flew out for a corner.
Instead, it was the Buddies who made the breakthrough in the fourth minute with Brophy reacting quickest to a flick on from Curtis Main to clinically drill a shot past Dundee goalkeeper Adam Legzdins from just inside the box.
The home side were then forced into an early substitution 13 minutes later with striker Danny Mullen having to be carried off on a stretcher after falling awkwardly and he was replaced by Cummings.
St Mirren had a chance to extend their lead when the Dundee defence was opened up once more but this time, Legzdins made a point-blank stop to deny Main.
Shortly after, Cummings had an opportunity of his own but Buddies goalkeeper Jak Alnwick dove full length to his right to tip the ball to safety.
The Dark Blues finally equalised on the stroke of half-time with Paul McMullan swinging a corner in from the left with the unfortunate Shaughnessy heading into his own net.
However, St Mirren took the lead once more, nine minutes after the break.
The Buddies' Jay Henderson fell in the box under a challenge from Cummings with referee Craig Napier pointing to the penalty spot.
The official then had to step in as the enraged Dundee striker confronted Henderson and – once the dust settled – McGrath stepped up to calmly slot the spot-kick low past Legzdins.
However, Cummings responded just six minutes later, sweeping home a great low cross from the left from Jordan Marshall to draw the Dark Blues level once more.
The home side were then reduced to 10 men in the 69th minute when Anderson chopped down Brophy as he broke clear from inside his own half.
However, Dundee held on to salvage a point.