Striker Martin Gritton's 13th goal of the season clinched Torquay's first Devon derby double over Exeter City for 40 years.
Gritton pounced in the 28th minute as Exeter momentarily stopped, expecting referee Tony Bates to blow for an infringement.
Gritton dashed clear on Alex Russell's through ball and drove a left-foot shot past advancing Exeter keeper Kevin Miller.
It took a brilliant double save by Torquay keeper Kevin Dearden to deny Sean Devine and James Coppinger just before half time.
And Torquay then owed a rare clean sheet to some brave defending by Lee Canoville and skipper David Woozley in the closing stages.
But the promotion-chasing Gulls still created the better second-half chances, with substitute Jo Kuffour always threatening in counter attacks.
Eight minutes from time Torquay winger Kevin Hill nearly forced the clincher when Exeter full back Scott Hiley cleared his shot off the line.
Torquay boss Leroy Rosenior said: "Maybe we got a lucky break, but we played on and didn't stop. Exeter made the mistake of stopping.
"Exeter are very disappointed, but I do think we were the better side - we had a bit more quality in creating chances.
"I don't know how Martin Gritton kept going like he did. We asked him to chase down their goalkeeper's kicks and he did it all night.
"They all worked hard, but Martin absolutely deserved his goal." Exeter manager Neil McNab described the goal's build-up as decisive.
"It was a diabolical decision to play on, and it's cost us the game," he blasted.
"Torquay are a decent side and they are in the play-offs, but I don't think there's a lot between us.
"I thought our lads were brilliant and we certainly deserved to get something out of the game."