In search of a desperately-needed win, Grays looked like they would have to settle for a point in Tuesday's Nationwide Conference clash but sucumbed to a devastating late blow when Billy Jones snatched a last gasp winner that gives boss Justin Edinburgh a real relegation headache.
Former Leyton Orient trainee Jones smashed an explosive drive beyond the despairing reach of Ashley Bayes five minutes into added time.
It was a gut-wrenching moment for the boss, his team and travelling supporters who had made the long trek to Devon and he might well have rued the decision five minutes earlier to change his defence by taking off Tom Kemp in a bid to waste time.
Changing players in the last minute is a move that often back-fires as newcomers struggle to get to grips with the pace of a match and it is a wonder, when a late goal is conceded so often, that managers stick with the tactic.
The Blues looked to have snatched a point from their trip to St James's Park when Glenn Poole produced a fine finish to stun the home supporters.
Paul Buckle has given the play-off chasing hosts a first half lead and after Bayes had pulled off a string of second half saves, the game seemed to be heading for a draw until Jones' late intervention.
It proved virtually the last kick of the game and there was no time for Edinburgh's men to try and salvage an equaliser.
He now faces the task of lifting his side for Saturday's FA Trophy semi-final first leg with Stevenage and former boss Mark Stimson, whose side warmed up themselves with a 1-0 win at Woking.
But of more long term imporatnce could be that Blues lost the chance to put some distance between themselves and the relegation zone and they now sit perilously just one place above the drop zone on the same number of points as fourth bottom Altrincham, who had a 5-0 morale-boosting win against Cambridghe, while thrird from bottom Tamworth have a game in hand and would overhaul Grays if they won it.
While Grays will rue the result, the win for the home side was really no moe than they deserved after they dominated much of the match, particularly the second half.
Despite a drying day that saw the match escape postponement, the early even brought a wave of showers that left the pitch as a quagmire.
Exeter adapted better to it in the early stages and went close early on when Jon Challinor toe-poked the ball wide after Billy Jones had picked him out.
At the other end Rob Edwards came to City's rescue thanks to an important headed clearance to deny Leroy Griffiths a free header in front of goal.
Chris Todd almost got on the end of another Exeter attack with an acrobatic lunge before Grays then strung together a scintillating sequence of passes which ended with Poole firing over the bar.
Bayes, a one time favourite of the Exeter fans, kept Grays in it with a couple of good saves but he was helpless when his former teammate Buckle put the Grecians ahead with a cool finish on 38 minutes after good work by Jamie Mackie, who had recovered sufficiently from illness to win his place back in the home side.
Grays had the last word of the first half when John Martin fired a shot just past the post and it wasn't long after the restart that the visitors got back on level terms after a combination play that started with Cameron mawer's low cross, a piece of initiative by Griffiths to tee up Poole and cracking finish from the Grays flanker that thumped into the net off the underside of the crossbar.
Substitute Adam Stansfield was introduced to liven up Exeter and he almost made an immediate impact when Bayes sliced Ben Harding's back pass into his path but the keeper made amends with another great save.
That was the catalyst for a sustained sequence of exter pressure when bayes again proved his value to the Blues and it looked as if his heroics had done enough to save a point until Jones delivered his late, late 20-yard thunderbolt
Thanks to the Thurrock Gazette for the report.