Harlequins stunned four-time champions Toulouse 31-24 on Sunday to reignite their European Cup quarter-final hopes just a week after the French rugby giants had seemingly delivered a fatal blow on the English side.
Harlequins out-scored their hosts three tries to two and bravely hung on in the closing stages when they were reduced to 14 men following a yellow card for No.8 Nick Easter.
Ahead 15-10 at the break, courtesy of Mike Brown and Joe Gray grabbing tries to Yoann Maestri's lone reply, Toulouse briefly took a 19-15 lead in the second period.
But full-back Brown added his second try against the run of play for a 20-19 advantage which soon became 25-19 thanks to the nerveless conversion and penalty kicking of former All Black Nick Evans who ended with 16 points.
Toulouse scrum-half Jean Marc Doussain cut the deficit to just one point with a try 11 minutes from time, but dogged defence and two late Evans penalties gave Harlequins a famous victory.
The French side still lead Pool Six with 13 points while Quins are a point further back with two games to play.
"We knew we had to win here to stay in the European Cup. It was do-or-die," said Harlequins skipper Chris Robshaw whose side lost 21-10 at home to Toulouse last weekend, a defeat which ended their 14-match unbeaten run.
Meanwhile, two-time champions Munster maintained their perfect record with a fourth successive win by seeing off the Scarlets 19-13.
Northampton, last season's runners-up, crushed Castres 45-0 to record their first win after three defeats in Pool One.
Greig Tonks, Ben Foden (2), Mike Haywood and Vasily Artemyev all scored tries for the Saints.