Exeter gave Harlequins a lesson in finishing and put a large dent in their play-off prospects by equalling the Premiership record of six successive bonus point victories.
Three opportunist tries – two from Lachie Turner and the other from Henry Slade - in the final quarter decided this pulsating contest and left Harlequins five points adrift off Leicester and Bath – who play on Saturday – with only two games left in the race for fourth place.
Harlequins scored a try early in each half but they struggled to convert further pressure and, on this occasion, they did not have the excuse of being without key players.
For much of the season Harlequins have been crippled by injuries but, with openside flanker Luke Wallace back from a three month lay-off, they were able to enjoy the rare luxury of being at close to full-strength for this crunch fixture.
They could hardly have made a better start either with number eight Mat Luamanu ploughing over in the third minute, his second involvement in a flowing attack that rattled Exeter.
But Exeter were not down for long. Loosehead prop Carl Rimmer made a nifty break that put Harlequins on the back foot and when they were sucked offside under pressure, Henry Slade slotted the penalty.
Exeter required the intervention of Olly Woodburn to save them when the wing snaffled a floated pass from Danny Care with a clear overlap and they again returned with points the next time they ventured into Harlequins’ territory.
This time it was left wing James Short who made the initial thrust with Dave Ewers muscling his way over from close range at the ensuing ruck.
Exeter immediately put themselves under pressure when Kai Horstmann knocked on as he picked up at a defensive scrum but a crunching tackle from Rimmer on Marland Yarde was followed by an uncharacteristic fumble from Mike Brown.
Harlequins had to settle for a simple penalty from Nick Evans, when Exeter drifted off-side in defence, to level the scores and reward them for their patience. Having absorbed the pressure, Exeter again proved outstanding in attack.
A hoisted kick from Slade bounced favourably for Short whose diagonal runs was supported by Woodburn. Brown and Tim Visser followed Woodburn who popped a neat inside pass to Michele Campagnaro who was left with a clear run to the line.
Slade tagged on the conversion but Harlequins stuck to their task and Evans reduced the deficit with another penalty on the stroke of half-time.
Within two minutes of the re-start, Harlequins were ahead after Evans conjured a try from nothing, stepping out of a weak tackle from Campagnaro close to half-way and beating the cover defence in a dash to the line.
The try was scored too far out for Evans to add the conversion but Slade made no mistake when he found the target after Jamie Roberts was punished for tackling a man without the ball.
Exeter should have added scored again when Harlequins lost possession in attack and Campagnaro broke free only to ignore Short outside him.
Whether the try would have been allowed to stand is debatable as Slade appeared to knock on when attempting to scoop the ball at the start of the attack.
Harlequins would argue that justice was done when Evans kicked his third penalty after Exeter were drawn offside from a series of pick and drive attacks in which Chris Robshaw was prominent.
Two tries in the space of four minutes stunned Harlequins with Turner and Slade both following up their own chips and Turner rubbed salt into the wounds when Turner strolled through. Tim Visser’s last-gasp try came too late to salvage a bonus point for Harlequins.