Torquay substitute Niall Thompson had only been on for a few minutes when he thumped in a cross from the left that flew off the Daggers skipper and in to the back of the net.
Torquay top scorer Rene Howe had come within inches of an early goal, crashing his first-minute volley off the crossbar from the left after United made a lightning start.
And Howe had a big part to play when Danny Stevens' second goal in two games did put Torquay 1-0 up after 36 minutes. Keeper Chris Lewington failed to hold Howe's cross-cum-shot from the right, palming the ball on to the bar before winger Stevens pounced to drill the ball home from close range.
The Gulls' best move came on 30 minutes as they swept downfield with right winger Billy Bodin cleverly finding Howe, who powered past marker Doe before testing Lewington with a rising angled drive.