Hearts' Republic of Ireland international Alan Maybury picked the perfect time to open his goalscoring account.
The Hearts full-back had never scored before in senior football but after almost two minutes of injury time had elapsed he popped up in the Thistle box with a stunning winner.
Mark De Vries saw his effort blocked in a goalmouth scramble but the ball broke to Maybury and from a tight angle he hammered a volley beyond Kenny Arthur.
It was hard luck on the Thistle keeper who had produced a string of wonderful saves to deny Hearts in normal time.
Indeed it was a strange game for much of the goalmouth action came in the last five minutes.
Gerry Britton missed a glorious chance to fire the Jags in front when he shot wide from ten yards but Hearts couldn't believe that Arthur had somehow blocked from Andy Kirk at point-blank range.
Then former Hearts man Kenny Milne forced Scott Severin into a goal-line clearance before Hearts went up the park on the counter attack and Maybury grabbed that winner.
Partick's well organised defence had limited Hearts to shots from long range but Arthur did well to deny Gary Wales on a couple of occasions and also to deal with two left-foot strikes from Jean-Louis Valois.
But perhaps the Thistle keeperÂ’s best stops were from deflected efforts by Kirk and De Vries for he had to react quickly to keep his side in the game.
Having said that Alex Burns had the ball in the net twice for the Jags but on both occasions he had strayed offside.
Consequently the stage was set for Maybury to leave his mark on the game with his late, late effort.