|Northampton (17) 29|
|Tries: Ludlam 2, Isiekwe, Hutchinson Cons: Grayson 2, Mallinder Pens: Grayson|
|Harlequins (23) 49|
|Tries: Care, Earle, Brown, Dombrandt, Steele, Smith Cons: Smith 5 Pens: Smith 3|
Marcus Smith orchestrated Harlequins' first victory at Franklin's Gardens since December 2012 as Northampton's disastrous home form continued.
Smith set up two tries with precisely-weighted kicks and applied the coup de grace by scoring Quins' sixth try.
Danny Care and Nathan Earle gave Quins control before Mike Brown, Alex Dombrandt and Scott Steele scored.
Tries from Nick Isiekwe, Rory Hutchinson and two from Lewis Ludlam rescued Saints a losing bonus point.
It was Northampton's eighth consecutive home defeat - extending their worst run of the professional era - and they only made the score slightly respectable by exploiting errors with Quins 20 points up.
- O'Flaherty stunner helps Chiefs beat Bath
- Bears earn bonus-point win over Warriors
- Gloucester overpower Wasps at Kingsholm
The visitors dominated the game and, with Smith swiftly directing their attack, kept the ball alive with clever offloads and neat handling - a feature of all their tries - to bounce back well from an opening round 33-3 defeat at home to Exeter.
With a 23-17 lead at the break, Smith's pinpoint kicking helped grow the advantage into an insurmountable one.
His grubber found full-back Brown down the right wing and a penalty soon followed that Quins took quickly from under the posts before Care's delayed pass sent Brown over.
A second Smith kick, this time cross-field to the right wing, was gathered by number eight Dombrandt and he powered his way over for the bonus-point score.
And with the final play of the game, Smith took Andre Esterhuizen's offload and skipped round two defenders to cap off a tremendous afternoon for the Harlequins fly-half.
Northampton director of rugby Chris Boyd:
"We spent most of the 80 minutes chasing the game. We got ourselves back into it just before half-time and then got to within eight points, but they controlled the game significantly better than we did and to concede six tries in the end was really disappointing.
"They did well but we also didn't execute accurately what we knew was coming all week, so it's really disappointing that we conceded three or four tries down that wide edge when we had planned how to deal with it all week."
Harlequins head of rugby Paul Gustard: "In any rugby team, you need a blend of experience, who have been there and done it, and there aren't many people who have done it more than Danny Care or Mike Brown. I thought both were exceptional today.
"Scott Baldwin, who has 30-odd caps for Wales, again was exceptional and you need that. Hugh Tizard is 20 and making his first Premiership start today and you need those kind of guys around him.
"I thought Danny Care, in particular, his game management was awesome, Scott's set-piece was excellent and Mike Brown just did what Mike Brown does at full back: counter attacks, claiming high balls. I was really happy with the spine of the team today."
Northampton Saints: Mallinder; Tuala, Proctor, Francis, Collins; Grayson, Mitchell; Waller (co-capt), Marshall, Hill, Ratuniyarawa, Ribbans, Isiekwe, Ludlam (co-capt), Wood.
Replacements: Fish, Auterac, Franks, Coles, Adendorff, Taylor, Dingwall, Hutchinson.
Harlequins: Brown; Earle, Northmore, Esterhuizen, Murley; Smith, Care; Garcia Botta, Baldwin, Louw, Young, Lewies (capt), Lawday, Evans, Dombrandt.
Replacements: Gray, Els, Kerrod, Tizard, Chisholm, Steele, Lang, Marchant.
Referee: Thomas Foley.