Cobus Reinach scored a stunning intercept try as Saints secured a crucial 32-6 Gallagher Premiership win at Worcester Warriors on Friday night.
South African scrum-half Reinach raced from well inside his own half, using his incredible speed to beat all Worcester cover to the try line.
It was a huge moment in the match as the Warriors, who struggled to gather any momentum throughout in an error-strewn, ill-disciplined display, had finally started to apply some second-half pressure at 12-6 down.
And after Piers Francis converted, Dan Biggar added his fifth and sixth penalties on a perfect night for the fly-half.
Luther Burrell put the seal on proceedings, delivering another intercept try as the Warriors crumbled in front of their own fans.
It was a vital victory for Saints, who had gone into the game sitting 10th in the league standings, having lost to Sale and Newcastle in their previous two matches.
They were locked on 17 points with Worcester but now move four clear of the Warriors ahead of next Friday's home game against Exeter Chiefs.
Duncan Weir set the tone early on for Worcester at Sixways as the fly-half booted the ball straight out from the kick-off.
Saints immediately got on the front foot and they thought they had scored on six minutes after some nice work from Burrell ended with a flying finish from Taqele Naiyaravoro.
But Worcester had just managed to ensure the big Australian's foot was in touch when he grounded the ball.
Saints were in front soon after though as more pressure paid off with a Biggar penalty.
Worcester were straight in Saints' faces from the restart, winning a penalty at the scrum, but Weir sent his effort wide.
Biggar made his opposite number pay at the other end, landing another penalty after Worcester continued to get on the wrong side of the referee in defence.
And Biggar was on target for a third time as Saints' strong start got even stronger.
The Worcester supporters, who had been quiet during the early stages, tried to rally their troops, resulting in a home surge, which forced Naiyaravoro into a rushed clearance.
And when the ball was put back in play, the Warriors did enough to earn a penalty in front of the posts, with Weir kicking it to cut the gap to six points.
Biggar had the chance to respond with a drop goal, but having initially let the ball slip from his grasp, his quick effort went to the left of the posts.
But he was on target soon after as Saints continued to fizz the ball around, dominating possession and forcing Warriors to infringe once again.
Weir had the chance to respond before the break, but he missed with the final kick of the half to leave Saints with a nine-point lead that was no more than they merited.
But Weir was to make up for his late first-half miss with a successful penalty early in the second period, after David Ribbans' back-chat pushed Barnes to move the kick forward.
Saints then lost Biggar and Tom Wood to knocks after they were both involved in collisions with former Northampton man GJ van Velze.
And Worcester looked certain to score when they flew forward, but Reinach scrambled to deliver a superb saving tackle.
Saints were under real pressure, but they were handed a huge reprieve as Reinach intercepted a pass on the edge of his own 22 and used his pace to win the race to the line.
It was a massive moment for the black, green and gold, and Francis, now on kicking duties, slotted the conversion to make it 19-6 with 20 minutes to play.
Biggar returned after passing his head injury assessment, boosting Saints further, and he was on the mark with another penalty after Heinrich Brüssow's chargedown forced Worcester to panic in defence.
Biggar was at it again with the boot just before the end as he landed yet another penalty, having just hit the post with a drop goal attempt.
And Worcester gave Saints the ideal conclusion to the game, presenting them with another intercept try as Burrell somehow found the energy to fly over the line.
Biggar converted and Saints almost scored on the counter again before the end, but they were more than happy with their sizeable Sixways success.
Worcester Warriors: Pennell; Heem, Venter, Mills (Lawrence 68), Adams (van Breda 79); Weir, Hougaard (Arr 79); Black (Waller 61), Singleton (Taufete'e 68), Schonert (Milasinovich 61); Bresler, Fatialofa (Phillips 63); Mama (Hill 49), Lewis, van Velze (c).
Saints: Tuala (Dingwall 75); Collins, Burrell, Francis, Naiyaravoro; Biggar, Reinach (Mitchell 75); Waller (cc) (van Wyk 62), Hartley (cc) (Fish 78), Hill (Franks 54); Ribbans (Ratuniyarawa 68), Lawes; Wood (Brüssow 53), Ludlam (Gibson 61), Harrison.
Referee: Wayne Barnes