Cummins took two wickets in two balls and had England 2-0 in the first over of the final innings late in a day already so full of astonishing Ashes feats it ensured this series would be one of the best ever.
When Cummins removed England captain Joe Root for a duck, his third of the series, it was a hammer blow to the home team having already been set another record chase of 383 to win.
England finished the day 2-18, and would need a Manchester miracle, or another superhero effort from Ben Stokes, to avoid losing the Ashes with 98 final day overs, and the forecast is fine, for Australia to bowl them out.
Cummins' dusk heroics came after England again looked helpless in the face of more batting magic from Smith who fell short of a fourth series century but still pushed the home team to the brink of total exasperation.
Smith was out for 82, a ninth consecutive Ashes half-century, caught while trying to slog spinner Jack Leach in to a nearby suburb as part of an attempt to bat England out of the game.
With memories of the Headingley miracle fresh in Australian minds, after England chased down 378 to win, the Aussies went hard in their second innings before captain Tim Paine eventually declared with his team 382 runs ahead, and the home team trying to waste time in fading light.
Smith’s effort was more marvelous because he first had to rescue his team from the mire when they fell to 4-44, after Mitch Starc and Cummins combined to dismiss England for 301 just after lunch.
With Matthew Wade (34), Smith put on 105 crucial runs, keeping England's bowlers at bay and taking Australia’s lead towards 350 with an array of shots which drew head-shakes from everyone at the ground, and every Englishman on the field.
Smith had his way with the bowlers in a manner no other batsmen could, playing such an eclectic variety of unorthodox shots that Root was moving his fielders nearly every ball.
There was an air inevitability as Smith passed 50 again, and a sense that he was only ever going to get himself out, which was what eventually happened.
Smith’s return to Test match cricket after 12 months out has netted him a staggering 671 runs, at an average just under 135, and a place beyond comparison to any of his peers.
It could not be a more different situation for his former vice-captain Warner, who was out for a third consecutive duck, LBW to Stuart Broad, having lasted just six balls.
Warner started the series smiling with good humour as he fended off fans calling him a “cheat” for his involvement in the "Sandpapergate" scandal.
But now the 32-year-old will have to fend off questions about his once unquestionable place in the side.
He lasted just eight balls for the game, after a second ball duck in the first innings, his third in a row after a second ball failure at Headingley.
Warner was out LBW to Stuart Broad, victim to the English seamer for the sixth time in eight innings. He has just 79 runs for the series and 61 came in one innings.
The pair of zeros in Manchester was the first in Warner’s 77 Test career and the first time since Graeme Wood in 1980 that an Australian opener was dismissed for three ducks in a row.
His opening partner Marcus Harris didn’t fare much better, out for six, as Australia’s poor run of opening partnerships continued.
Their twin failures came after Starc justified his selection with three new ball wickets at the beginning of the day which put England on the back foot early.
Starc dismissed both Jonny Bairstow and Ben Stokes, within three overs, before Pat Cummins helped close out the England innings at 301, just avoiding the follow-on.
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What a remarkable day of cricket!
Australia are eight wickets away from retaining the Ashes after a wild day four at Old Trafford in which Steve Smith toyed with England before Pat Cummins ripped them open.
England resumed their innings five wickets down, but were nearly skittled by lunch after Mitchell Starc (3-80) found his zone. The home team finally fell for 300, conceding a 197-run first innings lead, before Jofra Archer and Stuart Broad ripped through the shaky Australian top order.
Smith, however, proved he’s a man playing in a different stratosphere with a remarkable 81 to stabilize Australia’s innings and set England an unlikely target of 383.
That target looked a world away when Cummins removed Rory Burns and Joe Root in consecutive balls to reduce England to 0-2 in the first over – before they recovered to finish the day 2-18.
England require a further 365 for an improbable victory – but more likely have to survive 98 overs tomorrow to send the series 1-1 to the Oval.
Final over of the day and it will be bowled by MItchell Starc.
Starc got things going today by knocking over Jonny Bairstow and Ben Stokes.
Can he finish strong?
He throws the first three up full, but can't tempt Denly into a shot.
Final over of the day and it will be bowled by MItchell Starc.
Starc got things going today by knocking over Jonny Bairstow and Ben Stokes.
Can he finish strong?
He throws the first three up full, but can't tempt Denly into a shot.
After the drama of the first over, England have survived two more…
The England fans – bless them – cheered with delight as Jason Roy nurdled one to the legside for two.
They are off the mark!
A further boundary takes them to 2-6 after three overs.
Timewasting has gone into overdrive now. England could be in trouble for that after the day's play – but if they escape without losing another wicket it might be worth it
Unbelievable scenes at Old Trafford!
An absolute gem from Pat Cummins, hits the top of off stump. Root's second golden duck of the series.
Cummins is on a hattrick.
Amazing start for Australia and England are well and truly on the ropes.
Three balls in and Pat Cummins has the big breakthrough!
England's rock at the top of the order, Rory Burns, gets a leading edge and Travis Head takes the catch at mid off.
Horror start for England, and the perfect one for Australia.
No nightwatchman yet. Joe Root is in.
We'll get 30 minutes… and Pat Cummins has the new ball.
It is gloomy though – England will be desperate for play to be called for bad light.
England trying their best timewasting tactics here, and Paine has seen enough.
He races off the field with Australia's innings called on 6-186. That leaves a target of 383 for England to chase down.
Or a day to defend.
They'll have to face a tricky half hour here, too, with Starc, Cummins and Hazlewood steaming in.
England trying their best timewasting tactics here, and Paine has seen enough.
He races off the field with Australia's innings called on 6-186. That leaves a target of 383 for England to chase down.
Or a day to defend.
They'll have to face a tricky half hour here, too, with Starc, Cummins and Hazlewood steaming in.
What a catch! Another wicket falls and Australia are 6-158.
Wade departs for 34, slashing wide at one off Archer – to roughly where first slip might have stood.
Instead, it is snapped up in the left glove of Jonny Bairstow. Very impressive catch, that.
Wade is disappointed, and well might he be. He batted well in support of Smith today.
Mitchell Starc joins him at the crease, ahead of Cummins. Want him to tee off?
