Tim Swiel sent a last-gasp penalty attempt agonisingly wide in the driving rain at Sandy Park as Exeter Chiefs held on for a memorable victory.
Harlequins trailed at the break after an end-to-end first half, despite outscoring their hosts by three tries to one, with James Short’s late try and four Gareth Steenson penalties enough for a 19-17 lead.
And despite Tim Visser’s unbelievably fortunate score in the corner – with the ball coming back off the corner flag – the brilliant Steenson’s second-half try ultimately was enough for Exeter.
Exeter got off to a flying start with a penalty straight from the kick-off, with Harlequins offside after knocking on and Steenson made no mistake from the tee.
But the visitors hit back in emphatic fashion, driving up the field and winning a series of scrums on the Chiefs’ five-metre line before eventually being awarded a penalty try on seven minutes.
It looked at that stage like it could be a long afternoon for the Exeter pack, but after a massive scrum of their own, Steenson made it 7-6 three minutes later.
An Exeter mistake at the restart gave Harlequins a scrum, before Danny Care’s inch-perfect grubber was gratefully scooped up by Evans to touch down for Harlequins’ second try of the afternoon – although the No.10 could not convert from out wide.
Conor O’Shea’s side looked to press on and would have added to their score had their final pass not let them down, but it was Exeter who reduced the deficit after winning a scrum against the head and Steenson was immaculate again with his kick.
But not to be outdone, Harlequins twice turned down shots at goal to kick to the corner, and they were rewarded by their forwards as Charlie Walker went over for another try on 30 minutes after his side built the phases.
Evans once again could not find the mark from the touchline with his conversion, and after Harlequins coughed up yet another penalty for Steenson in their own 22, Exeter turned the game on its head with a score as the clock ticked into the red.
Reluctant to kick out into the wind Harlequins kept the ball in hand and paid the price when they were turned over, and quick ball across the backs let Short go over in the corner.
Steenson converted to send his side into the interval two points to the good, but O’Shea’s team talk clearly did the trick as Harlequins came out firing in the second period.
Exeter were pinged in the scrum on 42 minutes as the front-row went down and Evans put his side back into the lead.
Walker’s brilliant scything run then put Harlequins deep in Exeter territory, but strong defence from the home side saw them able to clear.
And Steenson was once again scourge of the visitors as he took his points tally over 20 with a try of his own – expertly picking up a bouncing ball in the wet after the referee played three penalty advantages.
Visser and Matt Hopper combined beautifully to go over and silence the home crowd, but after that try was chalked off for a knock-on, Elvis Taione saw yellow for Exeter with the TMO consulted.
And Harlequins made their extra man count immediately, although it was an incredible piece of luck that saw them manage a bonus-point try on 63 minutes.
Mike Brown’s grubber-kick was overhit, but remarkably bounced up off the corner flag and straight into Visser’s hands.
Harlequins again could not convert from the touchline in dire conditions at Sandy Park, and with the teams separated by just a point at 26-25 with ten minutes remaining the game was set for a grandstand finish.
Harlequins hammered away at the Exeter line, and despite desperate defence the hosts finally yielded a penalty in the 78th minute, with Tom Johnson sin-binned for coming in at the side.
However in the swirling wind Swiel could not make the incredibly tricky penalty attempt count, with his kick flying just wide of the uprights and Exeter clung on for the most slender of victories.