Craig Disley had given the hosts a first-half lead but the game was evenly balanced in the second period when James McKeown pulled off a world class save to keep out substitute James Rogers' stunning 30-yard volley.
Then, with just five minutes left on the clock, Disley fired in another speculative effort that visiting stopper Marcus Bettinelli spilled and allowed to creep over the line to give the Mariners a two-goal cushion. It was then left to Andy Cook to add the third just two minutes later and send Blundell Park into raptures.
A 3-0 home win had not looked on the cards for much of a tense, tight and entertaining affair on the East Coast. Indeed it was the visitors who had started the better of the two sides and they had a great chance to open the scoring in the first minute when Danny Harris burst into the area on the left side but his cut-back was cleared before the returning Harry Crawford, back at the Darts on loan from Barnet, could apply the finishing touches.
And Crawford was at the heart of all the visitors' attacks in the opening quarter hour, first cutting in on his left and firing wide and then flicking the ball over Shaun Pearson, before placing his volley straight at McKeown.
On 25 minutes the Mariners took the lead, arguably against the run of play, a corner routine went awry but the ball fell for Disley, 25 yards out, and he launched a vicious, swerving right-foot volley into the bottom right-hand corner.
Town's tails were up now and they surged forward, backed on by a vociferous home crowd. Brodie shrugged off two challenges and rolled the ball into the path of Derek Niven, who sent a low shot just wide of the target.
Niven and Disley then linked up well to release Cook in the right channel and he was denied by a fine one-handed save down low by Bettinelli. And five minutes before the interval the hosts should have made it 2-0. Marshall jinked his way down the left and crossed for Joe Colbeck, but the former Bradford winger placed his header over the bar with the goal gaping.
Into the second half and the Mariners were enjoying more of a territorial advantage, without really troubling the visitors' defence. Cook was receiving no protection from the match officials and Brodie was trying to muscle his way into shooting opportunities.
Then came McKeown's wonder save and the game sprung into life again. Town responded well to the increasing Dartford threat and on 85 minutes they got that all-important second goal.
Disley collected a throw from Sam Hatton and fired in an ambitious left-foot shot from 20 yards. It looked easy for Bettinelli but he spilled the ball over his shoulder and could only scramble back in vain as the effort crossed the line.
The noise level around Blundell Park went up another notch and the Mariners responded in kind with a third of true quality. Cook collected a long ball in the left-hand channel and twisted and turned in the penalty area, working an opening to fire low into the bottom corner.
A gallant Dartford side, who had more than played their part in the game, had lost their way and their misery was compounded when Lee Noble was dismissed for a late challenge on Aswad Thomas in the final minute of the game.