It wasn’t the first try. It wasn’t the second. Actually, it wasn’t even the third.
We already knew Lions and Wales Goliath George North was that good.
But it was what happened after that left a lasting mark.
First, the 22-year-old, who had moved from his preferred wide role to centre early in the match, displayed his astuteness.
From clearing up at one end, North was alert enough to clean up at the other, preventing Wales team-mate Dan Biggar from getting to his kick ahead first.
Having already registered a hat-trick, some players would have had their head in the clouds.
He held on to the ball so Saints could clear their lines and get back on the front foot in pursuit of a fourth try that could prove so crucial in the context of Pool 5.
And then he scored a try that brought Franklin’s Gardens to it’s feet, grabbing the ball and putting in a grubber kick that he proceeded to hunt down and dot down.
It was a moment of magic worthy of the extra point.
It was a try worthy of winning a game, never mind icing a cake that you played a large part in creating.
North, the British Bake Off fan, had cooked up a storm.
And the Gardens faithful feasted on that fourth try, lapping it up as their team bounced back from their defeat at Racing Metro with aplomb.
It was a stunning moment from North, who has produced a fair few in his short, highlight-saturated career.
And that it could mean so much in Saints’ bid to qualify for the quarter-finals of Europe’s top tier competition for the first time since 2011 made it even more special.
But let’s not forget the other 22 men who played their part in this victory.
Because while North was exceptional, extraordinary and any other superlatives you can find, there were other immense contributions.
On a feverish Saturday night at Franklin’s Gardens, Stephen Myler set the tone with his ever-accurate boot settling the nerves with an early three points.
And the fly-half, who had been named in the England EPS squad earlier in the week, proceeded to pull the strings with some impressive game management.
His lofted pass teed up North’s first score, while Ken Pisi’s cutting run played a huge part in the second.
Calum Clark was a menace at the breakdown - as usual - helping to suffocate Ospreys attacks with alarming regularity, and Courtney Lawes carried the fight.
There were many more big displays and that is what it takes to win at this level.
Saints had enough and more, as they have on each outing at the Gardens this season.
But this one was a bit special.
For North’s superman imitation, for the fact Ospreys had enjoyed seven wins in as many games going into the match, for Saints breathing new life into their Champions Cup bid.
It was a night few will forget in a hurry.
And it is one that will live with North for the rest of what promises to be one of the great Northampton careers.
How they rated...
Overcame his difficult night a week earlier with a cutting display. A couple of errant passes proved costly, but aside from that he did well... 7
His spring-heeled run left Ospreys trailing as North was sent over for a try. The Samoan is a stellar performer in a stellar side... 8
Had no time to make an impact as he was forced off with a head injury after just nine minutes... 6
Like Wilson, had to go off with an injury, but had more time to make his mark and produced a powerful performance... 7
GEORGE NORTH - CHRON STAR MAN
A display that defied belief as he switched from wing to centre and proceeded to score four tries as well as saving one. Pretty much the perfect performance... 10
A flawless showing from the fly-half, who landed everything point possible and steered the team in the right direction with some fantastic passing and kicking from hand... 9
Injected plenty of his trademark tempo into proceedings from the off, getting Saints on the front foot... 7
Was easily on top in the scrum battle as Saints dominated the set piece. Will be wondering how he was left out of the England squad... 7
The captain thought he had his first score of the season as he was sent over by Foden, but the TMO intervened. Nevertheless, a sound display... 8
Made one huge charge towards the line with the Saints fans roaring him on and the Australian enjoyed his night... 7
A massive performance from the lock, who carried brilliantly and stifled Ospreys with some fine tackling... 8
Celebrated an early try only to see it chalked off, but the lock won’t care as he excelled in the areas that matter most to him and the team... 7
Wreaked havoc at the breakdown, continually ruining Ospreys’ bid to push on. This was another huge performance from the England man... 8
Got his nose smashed for his troubles, but was relentless in his attempts to drive the team forward... 8
Was greeted with a warm round of applause as he entered the field on his 100th appearance for Saints, and produced another sizeable display... 8
Replacements (who played more than 20 minutes)
JAMIE ELLIOTT (for Wilson 9)
Got his chance early in the game as Wilson was forced off and he certainly took it with a lively display that kept Ospreys on their toes... 8
WILL HOOLEY (for Burrell 52)
Never looks out of place among such experienced company and stood up well as Saints pushed on for their bonus-point score they desired... 7
JAMES CRAIG (for Day 54)
Brought some freshness to proceedings and helped continue the huge forward effort that left Ospreys flailing... 6
GARETH DENMAN (for Ma’afu 56)
Saints were on top up front for the majority of the night and this was another good contribution from the prop... 6
KAHN FOTUALI’I (for L Dickson 58)
Probably didn’t get as long as he’d have liked against his old team, but he relished every second of it when he entered the fray... 6