Saints endured a second-half shocker as they slumped to a sobering 46-31 defeat to Newcastle Falcons at Kingston Park.
The Falcons scored five tries after the break, making it a total of seven on the day, as they recovered from a 24-15 half-time deficit to win it in style.
Saints had been as far ahead as 24-10 at one point, having flown out of the blocks, scoring three times, through Ken Pisi, Jamie Gibson and Harry Mallinder.
But the Falcons grabbed a try before the interval and were soon ahead in the second half as they cut through the Saints defence with alarming ease.
Scrum-half Sonatane Takulua enjoyed a fine day as he secured a hat-trick, rubbing salt in the Saints wounds.
The away side managed to grab a losing bonus point through Mike Haywood's effort, but it was scant consolation on what turned out to be a chastening Sunday afternoon.
Falcons move Saints in the Aviva Premiership standings, with Jim Mallinder's men now eighth.
They had looked set to rise up the table when they made a stunning start, with skipper Ben Foden setting up Ken Pisi, who glided in unopposed.
Stephen Myler added the extras and the Falcons fans desperately tried to urge their sluggish side to wake from their early slumber.
But the home side failed to respond and Saints stuck the knife in again soon after as Api Ratuniyarawa offloaded to flanker Gibson, who scored for the third game running.
Myler again landed the conversion with aplomb and Mallinder's men enjoyed a healthy 14-0 lead after just seven minutes.
The Falcons finally got going after winning a penalty at a Saints scrum, with Takulua slotting the kick to reduce the deficit to 11 points.
But Myler was soon restoring the 14-point advantage with a penalty as Saints continued to put the squeeze on the home side.
However, after Harry Mallinder ran into trouble 10 metres from his own line, the Falcons turned the ball over and had the way back into the game they desperately wanted.
Takulua was the man to find a gap and dive over after a wave of pressure, and the No.9 added the conversion to cut the gap to seven points.
Saints refused to be bowed though and they were troubling the Falcons every time they attacked.
Some superb skill from Ahsee Tuala and Pisi, who both offloaded in tight spaces, helped to tee up Harry Mallinder for a fine score out wide.
Myler was again assured with the tricky conversion from out wide and Saints were hunting the bonus point 10 minutes before the break.
But it was Falcons who grabbed the game's next try as prop Jon Welsh powered through the Saints defence and eventually Vereniki Goneva offloaded brilliantly for lock Sean Robinson, who scored in the corner.
Takulua hit the post with a tricky touchline conversion and Saints headed in for half-time 24-15 up.
But the Falcons made a stirring start to the second period, with prop Rob Vickers powering over for a try.
Takulua's conversion cut the visitors' lead to a precarious two points and the Falcons didn't waste much time in going ahead as they scored again almost immediately.
Sinoti Sinoti danced his way through and gave the pass to Takulua, who breezed in for his second try of the afternoon.
Takulua missed the conversion, but in just five second-half minutes, Saints had seen a nine-point lead disappear and now needed to respond at 27-24 down.
But the Falcons were flying forward and with Saints constantly missing tackles, havoc was being wreaked.
Pisi failed to stop Sinoti out wide and Takulua was again the beneficiary as he just managed to see off a last-gasp tackle from Foden to stretch and arm out and score.
The conversion was again missed, but Saints were now eight points down and really starting to struggle.
it was misery on misery as Kyle Cooper popped up to rub more salt in the wounds with a fourth try in what was turning into a horrible second half.
Joel Hodgson converted to make it 39-24 and Saints started to ring the changes.
One of their replacements, JP Estelles, made a big impact as he carried the team to within range and Haywood finished off the move to bag the try bonus point.
Saints tried to step it up further in a bid to get back in the game, but the Falcons defended with heart, with some of their players out on their feet after stopping a spell of pressure.
And there was even more cheer for the home faithful before the end as a lineout drive provided a fifth second-half score, with Mark Wilson the man to get it.
Takulua converted superbly, curling the ball through the posts from the touchline to put the gloss on a huge second-half showing and leave Saints staring a sizeable defeat.
Newcastle Falcons: Tait; Goneva, Waldouck, Socino, Sinoti (Watson 70); Hodgson (Delany 70), Takulua; Vickers (Harrison 76), Cooper (Lawson 70), Welsh (S Wilson 70); Green, Robinson (Olmstead 73); M Wilson, Welch (c), Latu.
Saints: Tuala (Estelles 68); K Pisi, Tuitavake (Hutchinson 76), Mallinder, Foden (c); Myler, Groom (Dickson 60); A Waller, Haywood (Clare 73), Brookes; Ratuniyarawa (Paterson 68), Day; Gibson, Clark (Nutley 68), Harrison.
Referee: Greg Garner