England 4-132 needing 259 to make Australia bat again
The Ashes is there for the taking on the final day in Perth and a crack in the WACA pitch looms as the key after a Mitchell Starc wonder ball edged Australia closer to regaining the sport's most treasured prize.
Steve Smith's men enter the fifth day of the third Test within touching distance of taking an unassailable 3-0 series lead and reclaiming the Anglo-Australian bragging rights they surrendered with defeat on the last Ashes tour of England in 2015.
It will take a stubborn rearguard action from the tourists or the forecast of rain to materialise as a deluge from above to stand between Australia and the urn.
England, 4-132 in their second innings, trail by 127 runs with Australia still to bat again if needed.
Australia's tilt at victory came with no small thanks to a jaw-dropping, unplayable ball from Starc that left James Vince (55) dazed and confused and his off stump airborne.
Delivered from around the wicket and wide on the crease, the left-armer's otherwise innocuous pill was heading down the leg side. Instead, it deviated sharply with the assistance of a crack in the pitch and crashed into the off and middle stumps, effectively a leg break bowled at more than 140kmh.
Josh Hazlewood, who had earlier removed Alastair Cook with a reflex return catch to continue the former captain's torrid tour, agreed it was the ball of the summer.
"I'd love five or six [of them] tomorrow," Hazlewood said. "It's just one of those ones that hits the crack and does a fair bit. You only need a couple to straighten up like that and you're in the game. It was a special ball."
That the ball changed its path so dramatically was out of the box but the fact that it struck the crack was no accident.
"We were obviously aiming at that crack from that end, as Jimmy [Anderson] did at the start of the day with a couple of lbws," Hazlewood said. "We're obviously hitting that, left-arm around and right-arm over, it's a pretty simple method. It's just about hitting that and getting it a bit up and down and sideways.
"There is not much more out there to aim out, to be honest, than that crack."
Vince, who had been shaping to flick the ball off his pads, could barely believe what he had seen. England's No.3 had been a key source of resistance with an excellent half-century and could not be held at fault. No right-handed batsman in the game could have kept this one out.
"I think if I face that another 20 or 30 times it'd get me out every time," Vince said.
"We'll have to have a look at that tomorrow. [Starc's] plan is pretty clear. He's going to come from wide of the crease and try and hit that crack."
It was a key setback for the visitors on an afternoon in which they had set about saving the series. They had been blown away at the WACA by Steve Smith and Mitchell Marsh's torrent of runs en route to an Australian record Ashes total at home of 9-662 (dec) that was topped up by the value adding of Tim Paine (49 not out)) and Pat Cummins (41).
Joe Root, out to Nathan Lyon's first ball, and Cook had already been lost to the cause, as had Mark Stoneman, also at the hands of Hazlewood, and the rocks-and-diamonds Vince appeared up for the assignment as rain approached and ultimately brought about a premature end to day four's play.
The 26-year-old's unlucky downfall left middle-order pair and first-innings centurions Dawid Malan (28 not out) and Jonny Bairstow (14 not out) with the task of being the bedrock of an England innings again, with everything on the line.
The Australians admit the prospect of weather intervening on day five is a concern but hope they can get enough of a shot at finishing off England.
"We've looked at [the forecast] a little bit," Hazlewood said. " I think there is just some rain tomorrow morning, so hopefully that doesn't hang around too long and we can get the best part of two sessions in or something like that to take these next six wickets."