It was a Wednesday evening where the Eden Gardens crowd didn't really have a dog in the fight, and in New Zealand, it was ungodly hours of the morning. So how many truly invested folks experienced that surreal batting from Finn Allen?

Perhaps, the Allen household. "I'm sure my parents were up watching the whole game. Hopefully they're proud," Allen said with a smile.

At 9:56 PM IST, or 5:26 AM Auckland time, when Allen struck the last of his 10 boundaries, South African shoulders dropped with the weight of this reality and the New Zealand dugout erupted with hugs and handshakes. In the middle, Rachin Ravindra had his hands in the air in celebration before jogging over to embrace the opener who had just used a stage as gargantuan as a World Cup semifinal to smash the fastest T20I century against a full-member team, and the fastest-ever in the tournament's rich history.

Those words tell you the story without sounding incredible enough - Allen had just scored a T20I 100 in 33 balls.

Besides those 10 fours, there were eight sixes - 88 of his 100 came just in boundaries, and he played only three dot balls. To call this a special knock would be the understatement of the tournament. And to grasp the improbability of the innings, you only have to look at how differently it began before gathering pace and getting launched deep into the night sky.

New Zealand perhaps, already had a foot in the final by the halfway stage of the semifinal. The dent from South Africa's wobbly start was too big to cover up even for the towering Marco Jansen, who rushed back to get ready to bowl the first ball after having tonked a face-saving 30-ball 55. Just three evenings ago, even West Indies learnt the follies of a slow start the hard way, and they had scored 26 more runs than South Africa's 169/8. Fast outfields and a skiddy surface as the evening wore on were always going to make South Africa's total look smaller than it already was. Allen just shrank it further, almost beyond recognition.

Five overs into the chase, New Zealand already had 62/0. But at that stage it was still about what Tim Seifert was doing to throw the South African quicks off their lines. As Allen would later attest, he had the 'best seat in the house' for that carnage. 41 of that 62 came off Seifert's bat and Allen had only played nine of the 30 deliveries until then. But as Aiden Markram brought on Corbin Bosch to finish the Powerplay, the switch flicked in the other direction.

Bosch started with a length loosener outside the off-stump and watched Allen smash it over backward point, his bat completing a full, swift arc over his shoulder. Bosch had an infinitesimal margin for error in an over where Allen decided to swing for the fences. New Zealand were already galloping ahead of the required rate, and Allen pushed for a gear somewhere above the stratosphere, determined to put the game well beyond doubt, if it wasn't already there. New Zealand had wiped out nearly half their target (84/0 in 6 overs, target: 170) and Allen had overtaken his equally adventurous batting partner after a 22-run over.

It wasn't just Bosch who suffered from the torment. Keshav Maharaj, coming back in after getting some rest in the inconsequential Zimbabwe game, was not spared of the cruelty either. In his over in the ninth, Allen reached a 19-ball fifty and then showed off his slick footwork, when he rocked back and pulled a ball that wasn't even very short, deep in the square leg stands.

Kagiso Rabada broke Seifert's stumps and, for a few seconds between the opener walking off and Rachin Ravindra walking in, South Africa found a brief moment of respite - a pause from the harrowing routine of retrieving balls from beyond the boundary. But that was all it was - a fleeting break in an ordeal for South Africa that felt both endless and like the quick rip of a bandaid.

It swayed more towards the latter from the halfway mark on, where Ravindra found himself on the 'best seat in the house'. From there he watched Allen flay Aiden Markram's bowlers, his fields and eventually his spirit, leaving the South African captain crestfallen before the result hit him and his team. New Zealand needed 46 off 60, but took just 16 of those available deliveries to send the best team of the tournament on their way.

Like he had done all evening, Allen picked up lengths early and had time to set himself up for shots that looked absurd in real-time. In one swift movement against Maharaj, Allen went deep into the crease and generated enough power to send a good-length ball sailing over long-on.

After a performance like this, there's a journalistic urge to find out what truly went on inside his mind while he was in the middle of that hitting trance. A quick "not much" said far more than the two words suggested. As he reached the climax of this absolute carnage in the 13th over, and managed to get his 100 with the winning shot, there were 39,000 fans cheering on.

Turns out, they did have a dog in this fight after all. For Allen, it goes down as an unforgettable night where he carried his team into an ICC final. And for those in the galleries, it doubled as a tantalising teaser - a glimpse of what could come in less than a month from now, when he swaps the black jersey for purple and gold.