Morton kept up their pursuit of Gretna but were fortunate to take all three points. Thistle manager, Dick Campbell, fumed that Christmas had come early for Greenock folk.
There was no early indication early that either side could dominate. Stephen McConalogue fired over as Thistle tested the home defence and 'Ton's only reply was a long-distance effort which Colin Stewart dealt with easily.
It was a surprise, therefore, when the visitors went ahead. Darren Brady's pass found McConalogue without a marker, and the striker promptly fired the ball past David McGurn from 12 yards.
Within a minute, Andy McLaren equalised. He attempted a shot from 16 yards and Stewart had it covered but Marc Smyth deflected it past the wrong-footed 'keeper.
McLaren had another shot held, but Graham Dorrans should have done better for the visitors with his header when Scott McCulloch found him with a crisp, accurate cross.
The second half was dominated by Morton, but they found Thistle's rearguard difficult to penetrate. Chris Millar had two efforts drift wide. Jim McAlister's shot was deflected into the path of Millar, whose shot was cleared for a corner and McLaren's cross from that corner was deflected wide by the narrowest of margins.
Ricky Gillies silenced the home crowd with a venomous curling shot from the edge of the box which crashed off the bar, but the winner came in bizarre circumstances. Stewart came out to make a headed clearance at the edge of the box but, inexplicably, he nodded the ball against the chest of Derek Lilley. The striker strode on to net assuredly.