Substitute Nigel Hasselbaink struck late to secure St Johnstone a deserved 1-1 draw with Scottish Premier League leaders Celtic at McDiarmid Park on Tuesday to bring to an end the champions six league match winning run.
Celtic, who had made just one change from the side that thrashed Dundee United 6-2 on Saturday, dominated proceedings in the first half as they battered the St Johnstone goal before Efe Ambrose headed them into a 37th minute lead.
But the home side improved after the interval and a marginal offside decision against Steven McLean denied them a 55th minute equaliser.
If the first decision had been questionable then there looked nothing wrong with Frazer Wright's 68th minute header from Liam Craig's free-kick but once again they were denied by the assistant referee's flag.
However, St Johnstone were not to be denied and with ten minutes remaining Hasselbaink curled a cracking shot past Fraser Forster from the edge of the box to earn his side their fifth point out of nine against Celtic this season.
Despite their winning run coming to an end the Glasgow giants increased their lead at the top of the table to 19 points after nearest rivals Motherwell lost 1-0 to Dundee United at Fir Park.
Celtic manager Neil Lennon was at a loss to explain how his side hadn't won. "The first half was the best football I have seen here under my tenure. We were absolutely magnificent and I don't think the scoreline reflects the performance," he said.
"How we didn't win the game is beyond me. We were absolutely awesome first half. But if you don't take your chances you always give teams a bit of encouragement."
His St Johnstone counterpart Steve Lomas admitted his side had been lucky early on.
"We rode our luck in the first-half between some great saves from Alan Mannus and some great blocks," Lomas said. "But we said to the lads to hang in there and all credit to the subs coming on as they gave us a major impact and Nigel scored a great goal."
Bhoys start strongly
St Johnstone were under pressure from kick-off and keeper Alan Mannus was kept busy as he twice denied Gary Hooper.
Lassad Nouioui was next to come close as he sent a glancing header just wide of the post from Emilio Izaguirre's cross.
The home side's first real chance didn't materialise until the 27th minute when Ambrose took a poor touch and allowed Mehdi Abeid to turn and fire in a shot on goal but the ball flew into the side-netting.
Wright was then the hero for the home side as he blocked Lassad's shot on the line after playing a one-two with Hooper.
Celtic's pressure finally paid off in the 37th minute when Ambrose gave them a deserved lead.
St Johnstone were caught napping at a short corner and Emilio Izaguirre swung the ball over for the Nigerian defender to head past Mannus for his second goal in two games.
St Johnstone started the second half brightly and thought they had grabbed a 55th minute equaliser when McLean stabbed home Abeid's superbly swung in free-kick from the left but his celebrations were cut short by the offside flag.
Much to the fury of the home fans St Johnstone had yet another effort controversially ruled out in the 68th minute for offside when captain Wright jumped highest to send a powerful header from Liam Craig's free-kick past Forster but the assistant referee had his flag up.
St Johnstone finally got the goal their play deserved lead in the 81st minute through Hasselbaink.
He gathered a pass from Abeid and spun away from Celtic replacement Thomas Rogne before curling a shot past Forster from the left edge of the penalty box.
Elsewhere, Johnny Russell ruined James McFadden's return to Motherwell as his first half strike earned Dundee United a 1-0 win.