Quins had their winning start to the season brought to an abrupt halt on Sunday as Owen Farrell led Sarries to a 18-16 win at the Stoop.
Harlequins had their winning start to the Premiership campaign brought to an end on Sunday as Saracens beat them 18-16 at Twickenham Stoop.
Sarries headed into the clash with the defending English champions on the back of a shock defeat to Exeter Chiefs, while Quins were riding high following an unblemished start to the season.
Things appeared to be going to plan for the hosts early in the match, with a third minute penalty from fly-half Nick Evans setting up an early advantage.
Sarries responded with Owen Farrell's first kick, though Quins quickly regained the lead following a second three-pointer from Evans.
Farrell then made it 6-6 on 20 minutes, and gave his side the lead for the first time in the match with another sweetly struck penalty on 34 minutes.
Quins appeared to be on the back foot when Olly Kohn was sin-binned for offside, but, despite the numerical disadvantage, the hosts were able to hit the front before half-time with the game's only try. Danny Care was the man to cross the try-line, hitting a gap in the defensive line to score, after what looked like a knock-on in the build-up was missed. Evans' conversion made it 13-9 at half-time.
Two penalties ten minutes apart from Farrell early in the second half put Sarries back in front, before Quins regained their advantage through a three-pointer from Evans, after George Kruis was sin-binned for not releasing.
Harlequins held their lead until the final six minutes of the match, but, when Evans' attempt at goal fell short, Sarries rallied. And their efforts were rewarded when a penalty handed Farrell the opportunity to maintain his 100 per-cent record with the boot and grab the spoils.
Pen: Evans 3
Pen: Farrell 6
Harlequins: 15 Mike Brown, 14 Seb Stegmann, 13 Matt Hopper, 12 Jordan Turner-Hall, 11 Ugo Monye, 10 Nick Evans, 9 Danny Care, 8 Nick Easter, 7 Chris Robshaw, 6 Tom Guest, 5 George Robson, 4 Olly Kohn, 3 James Johnston, 2 Joe Gray, 1 Joe Marler.
Replacements: 16 Rob Buchanan, 17 Mark Lambert, 18 Will Collier, 19 Charlie Matthews, 20 Maurie Fa'asavalu, 21 Karl Dickson, 22 Rory Clegg, 23 Ollie Lindsay-Hague.
Saracens: 15 Alex Goode, 14 Chris Ashton, 13 Joel Tomkins, 12 Brad Barritt, 11 Chris Wyles, 10 Owen Farrell, 9 Richard Wigglesworth, 8 Ernst Joubert, 7 Will Fraser, 6 Kelly Brown, 5 Alistair Hargreaves, 4 Steve Borthwick (capt), 3 Petrus du Plessis, 2 Schalk Brits, 1 Rhys Gill.
Replacements: 16 John Smit, 17 Mako Vunipola, 18 Matt Stevens, 19 George Kruis, 20 Andy Saull, 21 Ben Spencer, 22 Charlie Hodgson, 23 David Strettle.
Referee: Andrew Small
Assistant referees: Ashley Rowden, Andrew Pearce
Television match official: David Grashoff