Saints wasted a host of chances as Wasps won in Northampton for the second season in succession.
The away side were ruthless as they hit Jim Mallinder’s men with a sucker punch in either half to earn a 20-15 win at a stunned Franklin’s Gardens.
Saints enjoyed so much possession and territory throughout the game and had got off to a superb start thanks to George North’s early try.
But Wasps replied with a brilliant try from inside their own 22, with man of the match Jimmy Gopperth putting the finishing touches to it.
Gopperth added the conversion and two penalties before Saints’ replacement scrum-half finally made his team’s dominance pay with a clever score.
But Wasps, who were reduced to 14 men seven minutes from time when Nathan Hughes was sin-binned, were to win it with another eye-catching score as Dan Robson’s lightning-quick break and kick was dotted down by wing Josh Bassett.
Ken Pisi was yellow carded for tripping Robson in the build-up but after Gopperth converted, Stephen Myler slotted a penalty to secure the losing bonus point.
Saints have now suffered three defeats from their opening four Aviva Premiership matches, piling the pressure on Friday’s game against Exeter Chiefs at the Gardens.
Wasps on the other hand still have a 100 per cent record and moved to the top of the Aviva Premiership table, taking advantage of Saracens’ slip-up at Harlequins.
Wasps had headed to the Gardens on the back of a thumping 70-22 win against Bristol, but it was to be Saints who started the quickest.
After Kieran Brookes used his immense power to put Elliot Daly on his backside, the ball was moved left to North, who found himself with a free run-in to score.
Myler missed the conversion, but Saints had the beginning they wanted, to the delight of the home faithful.
Saints were then forced to do some defending as Wasps probed for an opening, and Mallinder’s men stood tall, forcing a knock-on to relieve the pressure.
And the home side were soon on the front foot again thanks to a Ben Foden kick that pushed his team up the pitch.
Wasps were clinging on by the skin of their teeth, with Saints a metre short of scoring for the second time after intelligent movement from Harry Mallinder.
But Saints were then hit with the ultimate sucker punch as Wasps used a scrum five metres from their own line to devastating effect, counter-attacking superbly to score.
Danny Cipriani’s clever grubber kick, which he gathered himself, started it all off and the ball was worked to Gopperth, who sprinted away to score.
Gopperth converted and Wasps had a lead that came as a surprise considering how dominant Saints had been.
Ken Pisi thought he had replied with a try on his 100th Northampton appearance, but his effort was ruled out for Alex Waller’s obstruction in the build-up.
Saints frustration was compounded when Wasps won a penalty at the breakdown and Gopperth landed it superbly to open up a five-point gap.
Wasps were to head in at half-time 10-5 up, but Saints continued to press from the restart, with Louis Picamoles seeing his offload, knocked on by Ken Pisi at the last.
It was agonising for the home fans, who were seeing their side huff and puff but just fail to blow the door down.
And again Wasps stung Saints as a scrum penalty provided another three points for Gopperth and an eight-point lead for the away side.
Elliot Daly had a chance to extend the lead after taking over kicking duties due to the distance of the penalty chance, but his kick from the tee was wide of the posts.
Saints’ discipline was really starting to let them down though, and so was their ball retention, with Wasps enjoying far more possession and territory.
Ken Pisi and Nic Groom had to be alert to stop Bassett racing in for a try that would have put the result beyond doubt.
Saints immediately went back up the other end, with a Mike Haywood grubber kick forcing Wasps to concede a lineout in the corner.
But as the ball was sent left by Saints, Myler’s pass was knocked on by Courtney Lawes, with a feeling of sheer disbelief shrouding the Gardens.
It was looking like it wouldn’t be the home side’s day, but after Hughes paid the price for persistent Wasps infringing close to their line, Saints had a man advantage.
And they immediately took advantage as quick thinking from Kessell saw the replacement scrum-half dummy before darting over himself.
Myler kicked the conversion and Saints were now just a point behind with five minutes remaining.
But again they were hit with a sucker punch as Robson broke with real speed and kicked ahead before Bassett won the race to score.
Ken Pisi was sin-binned for tripping Robson in the build-up before Gopperth converted to give his side a 20-12 lead with a minute remaining.
Myler secured the losing bonus point with a rapid reply in the form of a penalty, but Saints knocked it on in the final play of the game to give Wasps the win.
Saints: Foden (Tuala 64); K Pisi, G Pisi, Mallinder, North; Myler, Groom (Kessell 67); A Waller, Haywood, Brookes (Hill 66); Lawes, Dickinson (Paterson 54); Wood (c), Gibson (Harrison 54), Picamoles (Clare 68).
Wasps: Miller; Wade, Daly, Gopperth, Bassett; Cipriani (Eastmond 45), Simpson (Robson 53); Mullan (McIntyre 53), Taylor (Johnson 62), Cooper-Woolley (Moore 53); Symons (Myall 62), Gaskell (c); Jones, Thompson (Young 62), Hughes.
Referee: Luke Pearce