Dylan Hartley delivered a crucial try as Saints secured their first competitive victory under new boss Chris Boyd, beating Harlequins 25-18 at Franklin's Gardens on Friday night.
Hartley came off the bench six minutes into the second half and put the finishing touches to a trademark lineout drive to give Saints some crucial breathing space.
Harlequins had scored just a few minutes earlier, through England scrum-half Danny Care, cutting the gap to 12-10 in Saints' favour.
But that only served to sting Boyd's men into life as, backed by their supporters, they drove their way over the line.
Dan Biggar added the conversion and a penalty to his earlier four successful kicks at goal to help to make sure of his side's win.
A late James Lang try got the nerves jangling, but Harry Mallinder stepped up to land a penalty four minutes from time and Saints held on with some defiant defending to earn a victory that was greeted by a huge roar from the appreciative Franklin's Gardens faithful.
Saints had signalled their intentions to bounce back from the Gallagher Premiership opening-day defeat at Gloucester early on, flying out of the blocks and coming so close to a sublime score.
Ahsee Tuala gathered a high ball and offloaded superbly to release Tom Collins who turned on the turbos and closed in on the try line before a fantastic saving tackle from Quins fly-half Marcus Smith bundled the Saints wing into touch.
Smith was in the thick of it early on as he was soon forced to make a similar stop on Piers Francis in an identical area of the field.
And Smith was then in action at the other end as he landed the first points of the game, making the most of a penalty that was conceded by Alex Waller.
Quins were immediately penalised from the Biggar restart and Saints went searching for a try, booting a kickable penalty to the corner.
But the home side lost the lineout and, overall, they were far from secure in possession during the frenetic formative stages of the game, coughing up the ball far too often.
They again knocked on from another power-packed attack but referee Tom Foley pulled proceedings back for a penalty, and Biggar landed it to level the scores.
Ken Pisi was then forced off with a nasty-looking wrist injury, bringing Mallinder into the game after just 22 minutes, with Tuala moving out wide and Mallinder at full-back.
Biggar missed the chance to put his side ahead with a 40-metre penalty from in front of the posts but Saints continued to apply pressure with Heinrich Brüssow seemingly first to every breakdown, refusing to give Quins a second to rest.
Biggar made amends for his early miss to put his team ahead with a penalty after a high tackle on Francis.
Tuala was continually keeping Quins on their toes with some lovely breaks and with the home forwards earning penalties at the scrum, Biggar was able to land a third three-pointer before half-time.
Saints thought they had scored four minutes into the second half after a fine chip and offload from Mallinder opened the door for Cobus Reinach.
But the TMO deemed that the South African scrum-half had been held up and Quins breathed again.
The away team did soon concede a penalty for a no-arms tackle, and Biggar landed the kick to give his team some extra daylight at 12-3 up.
But Harlequins were not deterred and they finally managed to get a foothold in the second half with some patient build-up play resulting in a score for England ace Care.
Smith converted to cut the gap to just two points and the home fans felt the need to rally their troops.
And the players responded almost immediately, twice kicking penalties to the corner and eventually rumbling over the line, with hooker Hartley getting the score.
Biggar converted to make it 19-10 with 23 minutes remaining and the Wales fly-half soon added a penalty.
But Smith responded with a penalty of his own before Andy Symons was brought on for his Saints debut, replacing Luther Burrell.
Changes continued to be made and one was to have a huge impact for Harlequins as Lang was brought on for Smith and scored almost immediately, bursting through the attempted tackle of Biggar and racing over the line to dot down.
But Lang missed the conversion, leaving the gap at four points with seven minutes to go as the tension level started to rise.
Mallinder clamed the nerves slightly with a penalty after Biggar was relieved of his kicking duties having just taken a heavy knock and hobbled away.
And Quins then threw everything at Saints in an attempt to salvage a draw, but the home defence defence stood firm to force a knock-on that sealed the win and drew a massive cheer.
Saints: Tuala; Pisi (Mallinder 20), Burrell (Symons 65), Francis, Collins; Biggar, Reinach; Waller (c) (van Wyk 70), Fish (Hartley 46), Franks (Painter 57); Ribbans, Lawes; Haskell (Gibson 61), Brüssow, Harrison.
Harlequins: Morris; Walker, Marchant, Tapuai (Lasike 64), Earle; Smith (Lang 70), Care (Mulchrone 64); Marler, Elia, Collier; Symons (South 58), Glynn; White (Bothma 64), Robshaw (c), Chisholm.
Referee: Tom Foley