Northampton came to Ireland hoping to banish their Heineken Cup final nightmare but left even more traumatised after being denied in the most dramatic fashion possible.
The Saints seemed poised for victory as they held on to a one-point lead deep into stoppage time. Munster looked a beaten docket but came up with one final surge.
Saints were disciplined and kept Munster well away from goal but then Paul O'Connell's men built 39 phases of possession before Ronan O'Gara (pictured) sent a 40-metre drop goal straight into the swirling wind to snatch victory.
Saints coach Jim Mallinder said that frustration was the overriding feeling after the game and he was critical of the refereeing of Nigel Owens. "We have got a bonus point and we are still in the competition. But we felt we had a very good chance of winning and we would have perhaps if it was not for some refereeing decisions," Mallinder said.
Munster's coach Tony McGahan praised his men and said that O'Gara showed remarkable composure to nail the match-winning drop goal. He said: "He is a special person, to show the bottle and put his hand up and deliver that kick. I have never seen anything like it but it reflected well not just on him but also on the group."
Munster needed a good start after recent indifferent form and they got it by going back to basics, driving over from a five-metre lineout maul after just three minutes. Donnacha Ryan gathered the ball and Munster got the drive on to send Northampton back with hooker Damien Varley getting the touchdown. O'Gara added the conversion from the left wing.
But Northampton refused to be intimidated and full-back Ben Foden emphasised their composure with an array of skills from superb breaks to excellent offloads. It was no surprise when Munster's early lead was wiped out. A superb one-handed offload in the tackle by Vasily Artemyev put Foden away and he drew the cover down the left before sending Chris Ashton over in the corner.
Ryan Lamb added the difficult conversion to level the match after nine minutes and Northampton hit the front four minutes later when Lamb converted a penalty from the right.
In between Munster breaks, Northampton did most of the attacking with Lamb tacking on another penalty to make it 13-7 after 21 minutes when Varley was penalised for hands in a ruck.
O'Gara pulled back a penalty from 30 metres two minutes from the interval after Northampton were penalised in a scrum. That reduced the deficit to 13-10 but then in the final play of the half it turned Munster's way. After Murray made the initial break in midfield, Northampton halted the move, but Doug Howlett broke from the base of a ruck through the middle, dummied a pass to Ryan before rounding Foden and touching down beside the right post. O'Gara added the points and Munster, having been outplayed for large parts of the first half, led 17-13 at the break.
The sides exchanged penalties shortly after the restart after offsides following knock-ons, with O'Gara extending the Munster lead within a minute of the start of the second half. But Lamb was presented with an easier opportunity straightaway when BJ Botha handled after a knock-on by Johne Murphy and Ryan.
As the tempo rose it was Northampton who found a way through, James Downey striking a perfect line to get over despite the attentions of Howlett to make it 21-20.
Lamb missed the conversion as the swirling wind got stronger and caught a 40-metre penalty from O'Gara 10 minutes from the end. But then he struck his winner.
Munster J Murphy; D Howlett, D Barnes (W Chambers, 68), L Mafi, D Hurley; R O'Gara, C Murray (T O'Leary, 67); W du Preez, D Varley, B Botha (J Hayes, 70), D Ryan (D O'Callaghan, 54), P O'Connell (capt), P O'Mahony, J Coughlan (D Leamy, 67), N Ronan.
Northampton B Foden (G Pisi, 73); C Ashton, J Clarke, J Downey, V Artemyev; R Lamb, L Dickson (M Roberts, 67); S Tonga'uiha (A Waller, 69), D Hartley (capt), B Mujati (P Doran-Jones, 74), C Lawes (S Manoa, 67), M Sorenson, C Clark (P Dowson, 67), R Wilson, T Wood.
Referee N Owens (Wales).
Tries: Varley, Howlett
Cons: O'Gara 2
Pens: O'Gara 2
Tries: Ashton, Downey
Pens: Lamb 3