Three goals in thirteen second-half minutes secured second division survival for the Sons while at the same time sending the Red Lichties down to the basement league for at least a season.
While a point would probably have sufficed for Dumbarton, Arbroath knew that victory was probably essential to their survival hopes. But it was difficult to believe so much was at stake during a poor first half, the only highlight being a close-range shot by the home side's Iain Russell which hit the inside of a post before rolling along the goal-line to safety.
The visitors started the second period well, but although they were out of luck when an Alan Brazil effort from the edge of the box flew just wide, they also passed up several reasonable chances with Greig Henslee and Iain Diack being the major sinners on more than one occasion.
Dumbarton boss Paul Martin eventually made the brave decision to remove top scorer Russell and replace him with Chris Boyle. The move was far from popular, but he was vindicated within a minute when out of nothing Boyle sent a screamer past Craig Coyle from 25 yards.
Everything was now going the way of the Sons, and their nerves were calmed even further when Ryan Borris picked out the unmarked John Dillon and he strode unchallenged into the box before driving the ball across Coyle into the far corner.
Another substitute wrapped up the scoring, John Gemmell being left with time to pick his spot after the Arbroath defence had been exposed by another long ball from midfield.
Gemmell's goal was not just his first for Dumbarton, but also the first time he has found the net since scoring a winner against the Sons for Hamilton last season, a goal which denied his new club promotion. "I suppose I've kept them in the division two years running," he joked afterwards "but it was nice to be able to make amends to the fans who were really great today."
Defeated boss Harry Cairney felt that, yet again, his side's inability to score when on top cost them dearly. "It's been the story of our season, but I'm confident that if I can keep the nucleus of the squad together we'll be making a quick return to this division."