Australia's replacement pivot Mike Harris killed off Wales' hopes of keeping their Test series alive after slotting a last-gasp penalty kick to steal a 25-23 win in Melbourne.
It was a sad case of close but no cigar for the Welsh who came within seconds of winning Down Under for the first time in 43 years and set up a series decider.
However, Harris - on for Berrick Barnes - was called upon to provide the killer blow for the Wallabies after a maul was ruled to have been dragged down and Australia's New Zealand-born super sub didn't disappoint.
The defeat left a devasted Wales outfit once again reflecting on a golden chance gone begging in a thrilling encounter that saw the lead change hands nine times as the match went down to the wire.
The visitors showed their trademark fighting spirit at Etihad Stadium but the loss meant a series victory for Australia, who took out the first Test in Brisbane last week.
Wales got off to a the perfect start, launching a sustained attack after just three minutes which ended when wing George North side-stepped past Wycliff Palu and Rob Simmons to touch down.
Leigh Halfpenny kicked the easy conversion but the hosts went on to have the better of the half and Barnes kicked a pair of penalties to reduce their deficit to 7-6.
The diminuitive fly-half then made a crucial break on the stroke of half-time after slicing through a large gap between Sam Warburton and Ashley Beck, before coolly finding Rob Horne on his shoulder and the centre cruised over the line.
Barnes added the extras to make it a seven-pointer and the Welsh trailed 13-7 at the break.
However, the tourists once again started the better of the two sides after Ashley Beck and Jonathan Davies combined to show off their soccer skills by hacking the ball downfield when Will Genia's pass went astray.
Beck hit the deck, but Davies got a favourable bounce and calmly collected the ball near the line to score. Halfpenny once again added the extras and Wales were back in front (13-14).
Barnes booted a pair of three-pointers either side of a Halfpenny penalty and Australia were clinging to a 19-17 lead, but they then lost wing Cooper Vuna to the sin-bin for tackling Halfpenny in the air.
The Welsh full-back kicked the resulting penalty to put his side up 20-19 but the Wallabies went straight onto the attack and Barnes made it 22-20 when Wales infringed at a ruck.
The see-saw battle continied when the reliable Halfpenny was on target once again when Ben Alexander was penalised at a scrum 13 minutes from time before Barnes - who had been struggling with a leg injury - then put a kick wide of the posts with six minutes left.
But the Wallabies got another chance when, with the 80 minutes having elapsed, Richard Hibbard infringed at a driving maul, and Harris calmly stepped up to drill a tricky penalty straight through the uprights.
Man of the match: For Wales, Leigh Halfpenny kept his side in the hunt thanks to a flawless kicking display and perhaps would've been awarded this gong had Wales won. However, the official man of the match award went to new dad Berrick Barnes and it's hard to argue against it. Australia's number ten set up the Wallabies' only try of the match and contributed 17 points before being replaced.
Moment of the match: We're pretty sure every pub in Wales now have a picture of Mike Harris on the bullseye of their dartboards following the replacement's match-winning kick in extra time.
Villain of the match: Mike Harris - we were looking forward to seeing the series head into a decider next weekend! But we won't hold it against you... too much.
Pens: Barnes 5, Harris
Tries: North, Davies
Cons: Halfpenny 2
Pens: Halfpenny 3
Australia: 15 Adam Ashley-Cooper, 14 Cooper Vuna, 13 Rob Horne, 12 Pat McCabe, 11 Digby Ioane, 10 Berrick Barnes, 9 Will Genia, 8 Wycliff Palu, 7 David Pocock (c), 6 Scott Higginbotham, 5 Nathan Sharpe, 4 Rob Simmons, 3 Sekope Kepu, 2 Tatafu Polota-Nau, 1 Benn Robinson.
Replacements: 16 Stephen Moore, 17 Ben Alexander, 18 Dave Dennis, 19 Michael Hooper, 20 Nic White, 21 Anthony Fainga'a, 22 Mike Harris.
Wales: 15 Leigh Halfpenny, 14 Alex Cuthbert, 13 Jonathan Davies, 12 Ashley Beck, 11 George North, 10 Rhys Priestland, 9 Mike Phillips, 8 Ryan Jones, 7 Sam Warburton (c), 6 Dan Lydiate, 5 Alun Wyn Jones, 4 Bradley Davies, 3 Adam Jones, 2 Matthew Rees, 1 Gethin Jenkins.
Replacements: 16 Richard Hibbard, 17 Paul James, 18 Luke Charteris, 19 Justin Tipuric, 20 Rhys Webb, 21 James Hook, 22 Scott Williams.
Referee: Chris Pollock (New Zealand)
By Dave Morris