Munster edged the Scarlets at Stradey Park on Saturday, with a penalty deep into injury time handing the Irish an epic 24-23 Magners League win.
The Scarlets, who sacked director of rugby Phil Davies last Tuesday, had seemed destined to be on course for a morale-boosting win as they led 20-5 at the interval and 23-16 on normal time.
Paul Warwick launched the Heineken Cup finalists' dramatic comeback with a try on 86 minutes, but his touchline conversion rebounded off the right post.
But he made up for it with a penalty goal from inside his own half - the last kick of the game - to stun the home crowd.
Before the start all the talk at Stradey Park concerned both teams' coaches - Davies's dismissal and Munster's Declan Kidney, who is expected to be confirmed as Ireland's next coach.
It took the visitors just five minutes to score the first try. Home flanker Nathan Thomas lost possession on the floor and Munster moved the ball wide to the left, where wing Ian Dowling rounded opposite number Dafydd James and ran in from 60 metres.
But the Scarlets, playing with a strong wind at their backs, responded with a Stephen Jones penalty goal after centre Rua Tipoki had failed to roll away at a ruck. A second Jones effort from halfway, however, missed the target on 11 minutes.
The Scarlets were rewarded with a period of concerted pressure with a second successful penalty for Jones, which saw his side go into a 6-5 lead after Munster flanker was sin-binned for tackling a man without the ball.
And more pressure earned Scarlets a try for James who sidestepped his way over after a good build up from a scrum. Jones' conversion gave the Welsh region a 13-5 after 29 minutes.
With Munster still down to 14 men that became 20-5 as some dubious defence, including a missed tackle by Ronan O'Gara, allowed Matthew Watkins to breeze over.
Wallace returned to the field and looked as if he had made up for his sin-bin but having looked as though he was about to score with a kick and chase he knocked on under the posts.
Munster's cause was helped that O'Gara was successful with a penalty goal from the 22 after 46 minutes and on 52 Dowling went over for his second try after full-back Denis Hurley had exploited a gap in the home cover.
The Scarlets were given some respite when Jones converted a fine penalty into the wind from 35 metres out as the home side led 23-13. But that was cancelled out by Warwick's 68th-minute strike.
And Munster's last-gasp pressure told as Warwick was able to eat away at the Scarlets' lead.
For the Scarlets:
Tries: James, Watkins
Cons: S Jones 2
Pens: S Jones 3
Tries: Dowling 2, Warwick
Pens: O'Gara, Warwick 2
Scarlets: 15 Morgan Stoddart, 14 Dafydd James, 13 Gavin Evans, 12 Nathan Brew, 11 Matthew Watkins, 10 Stephen Jones (capt), 9 Gavin Cattle, 8 Nathan Thomas, 7 Gavin Thomas, 6 Dafydd Jones, 5 Scott MacLeod, 4 Vernon Cooper, 3 Deacon Manu, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Phil John, 17 Mahonri Schwalger, 18 Lou Reed, 19 James Bater, 20 Liam Davies, 21 Rhys Priestland, 22 Darren Daniel.
Munster: 15 Denis Hurley, 14 Doug Howlett, 13 Lifeimi Mafi, 12 Rua Tipoki, 11 Ian Dowling, 10 Ronan O'Gara, 9 Tomas O'Leary, 8 Denis Leamy, 7 David Wallace, 6 Alan Quinlan, 5 Paul O'Connell, 4 Donncha O'Callaghan, 3 John Hayes, 2 Jerry Flannery, 1 Marcus Horan.
Replacements: 16 Frank Sheahan, 17 Federico Pucciariello, 18 Mick O'Driscoll, 19 Donnacha Ryan, 20 Peter Stringer, 21 Paul Warwick, 22 Anthony Horgan.
Referee: Neil Paterson (SRU)
Touch Judges: Jon Mason (WRU), Alan Jenkins (WRU)