James Horwill had an eventful afternoon as his last-gasp try helped Harlequins end 14-man Saracens' brilliant unbeaten start to the season on a dramatic derby day in the Premiership.
Champions Saracens had won all eight league matches and their four European Rugby Champions Cup fixtures in an imposing start to the campaign.
But London rivals Harlequins brought an end to Sarries' dominance in a thrilling encounter at the Stoop on Saturday, Horwill crossing in the last minute in a game that also saw Rhys Gill sent off for the visitors.
Horwill's day had started poorly after he was sin-binned in the first minute for an ugly collision with George Kruis at the breakdown, an incident that saw the Saracens star taken from the pitch on a stretcher - although the club later posted on Twitter to say he was "up and about in the changing room".
In a high-action half, Harlequins twice hit back as Rob Buchanan and Nick Evans cancelled out Neil de Kock and Billy Vunipola scores.
Saracens' Owen Farrell and Quins' Ben Botica traded penalties as the lead changed hands, but the match swung in the hosts' favour when Gill was red carded for a dangerous tackle.
Botica's boot put the hosts ahead in the 73rd minute and Quins put the game beyond doubt when Horwill scored after Sarries lost possession deep in the opposition half.
There was more late drama as Leicester Tigers defeated Midlands rivals Northampton Saints 30-27 in front of 25,849 fans at Welford Road - a post-war record capacity crowd.
Leicester, who brought Manu Tuilagi off the bench for his first appearance since October 2014 due to a long-term groin injury, raced into a 21-0 lead thanks to scores from Matt Smith, Lachlan McCaffrey and Owen Williams.
However, Saints - who were without potential England captain Dylan Hartley through injury - showed their strength to come back into the match through tries from Teimana Harrison, George North and Jamie Gibson.
Freddie Burns' boot had kept Leicester in front, but it looked as though the match was heading for a draw when Stephen Myler split the posts for Saints late on. However, there was one more twist as Burns' last-gasp penalty won it for the Tigers.
Rounding off the action, Exeter Chiefs moved to within three points of Saracens at the top of the table with a 19-10 beating of Gloucester.