Chris Froome started the day at the Giro d'Italia three minutes and 22 seconds behind leader Simon Yates.
He finished it 35 minutes and 42 seconds ahead of Yates, and is sitting pretty in the pink leader's jersey with just two stages to go.
That's the astounding outcome from one of the most unbelievable stages in Giro d'Italia history; a stage which has turned the race on its head.
It was a performance from Froome beyond belief, a superhuman display of astonishing endurance. Call it what you will - all the normally hyperbolic descriptors today apply for a stage that will live long in the Giro history books.
Remarkably, Froome launched his winning attack with 80 kilometres to go. Nobody came close to catching him, as he coasted to a victory by a staggering three minutes to move into the race lead, 40 seconds ahead of Tom Dumoulin.
It will undoubtedly be a controversial win as well. Froome failed a doping test at last year's Vuelta a Espana, testing positive for excess levels of salbutamol. That case has still not been resolved, with some riders arguing he shouldn't even be competing at the Giro, and others no doubt drawing parallels between the two storylines.
Given cycling's history, remarkable feats always cause suspicion - for better or for worse - and there will be more drama to follow as we wait for the results of his pending case. Today though, that didn't seem to bother Froome as he stood atop the podium, having destroyed the rest of the peloton.
Amongst the wreckage left by Froome was Kiwi hope George Bennett, who crossed the line in 12th, 8.38 in arrears. He showed early strength, sitting ahead of several rivals, but was left in an unfavourable position on the road as his fellow contenders slowly came back and usurped him.
Not all of them did however, with Bennett moving up two spots into ninth overall on the general classification, 12.35 behind Froome. He is still well poised for New Zealand's first ever top 10 in Giro history, after jumping past Rohan Dennis, and the oh so unfortunate Yates.
For so long, Yates was by far the strongest rider in the race. He wore pink for 13 days, and was unmatched in the mountains for the first two weeks. He showed his first signs of weakness yesterday, losing 28 seconds, and after he had crested so many new heights, he couldn't handle the toughest one of all.
It was the Colle delle Finestre - an 18.5 kilometre slog at a steady 9.2 per cent gradient - which proved pivotal. Early on the climb, with 86.3 kilometres left in the stage, Yates was dropped, and his dreams of Giro glory were extinguished in an instant. Six kilometres later, after his Sky team had reduced the leading group to just six riders, Froome lit a fire behind his own quest for distinction.
He churned away on the picturesque mountain, splattered with snow which had been melted by the 26 degree warmth. On the road, it was Froome turning up the heat on his rivals, and Bennett found himself in the third group, following Froome and a separate group of five.
Normally, you'd expect the numbers advantage to work in the chasers' favour, but this was no normal stage. In the first chasing group, only two riders were committed to the chase, and the same problem plagued Bennett, who was eager to push on but was faced with resistance from riders who had teammates up the road.
All the bickering led to Froome racing away. He had 41 seconds at the top of the climb with 74 kilometres to go, two minutes with 50 kilometres to go, and somehow, three minutes with 22 kilometres remaining.
It was a staggering turnaround. Many people had expected Froome to abandon the race, after a horror first week featuring two crashes and significant chunks of lost time. At one point, he was 4.52 down on the lead, but now, he's on his way for a third consecutive Grand Tour victory.
The man best poised to stop him is Dumoulin, who did an extraordinary amount of work to try and limit his losses today. With Miguel Angel Lopez and Richard Carapaz shamelessly sitting on his wheel and not helping his cause, Dumoulin battled all day, and kept himself in with a chance of defending his title.
Bennett will surely feel for Dumoulin after the day he had. The Kiwi too was stronger than some of his rivals, but was forced to do the bulk of the work at the front of his group. That first led to an argument with Domenico Pozzovivo, then saw those rivals chase down, and finally, surpass him on the final climb.
The 28-year-old isn't just content for a top 10 finish, and a rise to seventh is a realistic shout on tomorrow's penultimate stage.
"I came here for a lot more," he said after the stage. "We have another day tomorrow."
It shapes to be another incredible stage. There are three tough climbs in the last 80 kilometres, and this time, everyone will have to attack Froome. Although, with the third-placed Thibaut Pinot 4.17 down, it would seem that Dumoulin is the only rider capable of catching Froome.
Before today, that statement could be made with conviction.
But, considering the madness on show today, anything is possible.
Niall Anderson is covering every stage of the Giro d'Italia live for the Herald. He will lord this stage over everyone who missed it.
Niall's Giro d'Italia wraps