Saints put in a punchy performance against rivals Saracens and Wasps to secure their place at Premiership Rugby Sevens finals day.
The youthful squad, which included the senior experience of Glenn Dickson and Teimana Harrison, will head to The Stoop next Friday after overcoming a slow start to progress.
Harlequins humbled the home side 42-7 in the night’s opening game, but Saints stormed back, finishing things off with a win against Saracens, that also included some fisticuffs.
That showed how much it meant to the passionate players in green, black and gold, who lapped up the sound generated by a crowd of more than 11,000 at Franklin’s Gardens.
And they will now be desperate to go all the way when they head to London for the showpiece occasion.
They will need the same resilience they showed after the first game, which saw them suffer from start to finish.
Quins dangerman Charlie Walker, who was bulldozed by George North in a league fixture at the Gardens last season, dived over to open his side’s account.
Quins were well fancied to do well and it was easy to see why as another of their hotsteppers, Ollie Lindsay-Hague, danced through the middle and charged over the line.
Louis Grimoldby converted and he was soon adding the extras to another score as Sam Olver nutmegged Glenn Dickson in attack and the ball went through the legs to Henry Cheeseman charged from his own half to score.
Cheeseman’s try grated on the home fans with one jokingly shouting ‘come on Saints, you’re rubbish’, and it wasn’t to get any better after the break.
Lindsay-Hague was just too hot to handle as he showed off his fleet-footed nature to weave his way through and grab his team’s fourth five-pointer of the night.
Grimoldby again converted and did so once more after Alosio Yamoyamo cruised through the porous home defence to make the score a massive 33-0.
And having spent most of the first game adding gloss to his team-mates’ tries, Grimoldby got one of his own - and converted it - to earn a huge 42-7 win for Quins.
Saints’ second game started in similarly sticky fashion as Wasps No.7 Tom Howe claimed a stunning score, kicking the ball from inside his own half, taking the ball on and scoring.
Harry Sheppard converted and Saints, backed by plenty of the 15-man first-team regulars, and GJ van Velze, who was back from Worcester for the night, again had a job on to get back into a game.
But this time they landed an immediate riposte as Rory Hutchinson replied, storming in and giving Mallinder the chance to level the scores with the conversion, which he did.
Wasps were in sevens heaven soon after, though, as Tom Bliss picked up the pieces to score in the right corner.
Sheppard put the men in blue 14-7 up at the break, but ‘oh when the Saints’ was soon blaring out as Harrison crashed over for the home side.
The conversion attempt was missed, but Saints were ahead soon after as Sam Olver joined the try-fest.
In a see-saw encounter, it wasn’t long before Wasps re-took the lead as George Eastwell wrote his name on the scoresheet, with Sheppard converting.
But there was to be a sting in the tail for the away side as Lewis Ludlam flew across the line to win it 24-21 for Saints late on.
The final game of the night saw the home side take on Saracens, who were greeted with a loud boo when their name was read out.
But, to the disappointment of the Gardens faithful, Sarries were soon ahead as, after Harrison had seen yellow, Elliot Reeder went over.
The conversion was successful, but Saints ate up the turf and responded through a Howard Packman score in the corner. Mallinder converted superbly.
And he was soon adding the extras again after a clever show and go from Tim Cardall secured a second try of the game for the hosts.
Xavier Bauwmans then saw yellow for Sarries, but it mattered not to the men in blue and grey as Kenyan speedster Ian Minjire did his best Usain Bolt impression, sprinting between the sticks.
That meant it was level at the break but Mallinder wasn’t prepared to let things lie and showed his passion with a roar after going over in the corner.
The No.12 added the conversion to the delight of the home crowd, who were again on their feet moments later as Ludlam picked up a high pass and darted over for another score.
There was to be a brawl before the end as both sets of players waded in to add fuel to the fire of the rivalry between the two clubs, but Saints had already done their talking on the pitch.
And they rounded off the night with another score, Packman getting it, to complete a 33-14 victory and guarantee the place at finals day.
Saints squad: Josh Skelcey, James Fish, Glenn Dickson, Tim Cardell, Alex Woolford, Rory Hutchinson, Lewis Ludlam, Teimana Harrison, Phil Robinson, Sam Olver (c), Howard Packman, Harry Mallinder.