Ten man Bray made valiant efforts to recover from a two goal deficit, but the task proved a touch beyond them.
Despite scoring twice after the dismissal of keeper Peter Cherrie early in the second half, through Aaron Greene and Ryan Brennan, they succumbed following a late third goal by Harps substitute Ibrahim Div-Keïta.
Eddie Dsane and new Harps signing Mark Timlin had done the damage midway through the first period and on the stroke of half-time respectively.
It was a night to forget for the Bray netminder, taking the pitch for a record-equalling 73rd consecutive league match only to leave after only an hour following a rash challenge outside the area on Harps young English striker Dsane, who was clear through.
Remarkably, Cherrie's red was the first card Referee Anthony Buttimer had shown in the course of a game which could, in other hands, have seen a penalty and at least two cautions by that stage.
Harps keeper Ciarán Gallagher, who had a very quiet game for over an hour, had nevertheless to come forward twice in the opening minutes to collect attacking long balls, and Ethan Boyle was warned for dissenting at the award of an early Bray free.
Wexford native Boyle, man of the match by any measure, cleared Karl Moore's fourth minute corner for a throw and barely two minutes later was himself feeding a long throw in a dangerous position from which Kilian Cantwell shot straight at Cherrie.
Another two minutes and the lively Dsane was menacing the Bray keeper, who had to race wide to clear, and two mintues further on he shot too high after a neat feed from former Bray man Seán Houston.
The Donegal side may have been dominant, but the Seagulls still had something to offer, skipper Conor Kenna heading on to the top of Gallagher's net, but looking dangerous in a studded challenge on Houston that failed to attract official attention.
Just after the quarter hour, from a Michael Funston corner, Boyle was on hand to head but Cherrie was also on hand.
Twenty minutes in, Houston stole possession in the Bray half but his final touch was poor, and past the right-hand post.
And when a Gary McCabe shot ricocheted out off Barry Molloy, the corner led to a Kenna effort that Gallagher just managed to get a touch to.
Moore's next flag-kick was eventually part cleared and chased by Hugh Douglas, but his return cross was claimed by the Harps keeper.
Harps' opening goal ultimately came from a fine ball by Paddy McCourt which put Dsane in behind Keith Buckley, and the striker fired the ball inot the far corner of the Bray net.
Shortly after that, Douglas stooped to head low and unfortunately met Houston's rising leg as both went for the same ball with different techniques.
The Bray man came off worse and had to leave the fray for medical attention. It was just the first of several blows for the home team.
Just after Tim Clancy replaced Douglas, a Bray attack ended with the ball out over the end-line, McCourt the last to touch it and a goal-kick awarded.
Greene shot just just over, and after McCabe found Brennan, Flood fired the latter's cross goalward and it took a desperate clearance by Boyle off the line to prevent an equaliser.
Caolán MacAleer took possession of a poor Bray ball and following a long run shot right of the target, getting the line right two minutes later but the height off this time.
With the visitors looking the more likely to score, Houston shot straight at Cherrie, who then claimed the cross at the end of Boyle's long-way-round solo move.
Nevertheless, a long ball by Greene found Brennan unmarked and clear but a pace away when Gallagher got there first.
But then wha seemed a fairly harsh free apparently for an all-but-inadvertent handball against Kenna 20m out turned into a score when the Bray wall inexplicably parted to admit Mark Timlin's set-piece ball.
It was just what Harry Kenny didn't need on the stroke of half-time.
McCabe didn't take the field for the second period, curiously replaced by Jason Marks, which hardly appeared to be an attacking decision.
Within minutes, no action was taken on a fairly late sliding tackle, and the offside flag was inexplicably raised against Dsane, but both teams, too, were guilty of blunders in the opening stages.
Following a Bray corner, Ciarán Coll cleared and Dsane went on a run to no great effect in the end.
On Bray's next attack, Gallagher took Brennan out of the action and got away scot-free.
Unfortunately, Cherrie's corresponding behaviour was even clearer, when MacAleer put Dsane in behind the Bray centre-backs and the Bray keeper, diving to claim, missed the ball but not the man.
The red card flourished straight away by Buttimer was inevitable.
Lee Steacy's first League appearance came at the expense of sacrificing Anto Flood, who had not been too convincing in his forward role.
And when Dsane himself eventually took the free kick from inside the “D”, it went out off the wall for a corner that came to nothing.
Within a minute, a Greene free found Mark Salmon, but his header lacked the power to get past Gallagher.
The ten men got a reward for their efforts five minutes later, however, when Moore passed to Buckley and the latter crossed for Greene to find the net from the right, and the home side intensified their play, Gallagher brought into action with a great save from Brennan, and a brace of corners keeping up the pressure.
Once more the offside flag dubiously thwarted a Harps attack, and then Ollie Horgan withdrew Dsane to replace him with the recently signed young Frenchman, who was less than a minute in action before scoring his first goal for his new club, heading home from Boyle cross.
Despite this further setback, Bray continued to press, a Brennan shot deflected over, and from Greene's corner kick headed down by Kenna where Brennan could stab it home.
But despite five minutes added, there wasn't any real opportunity for the Seagulls to contrive an equaliser.
Mícheál Ó hUanacháin
Bray Wanderers: 1 Peter Cherrie ; 6 Keith Buckley, 2 Hugh Douglas, 4 Conor Kenna , 10 Karl Moore; 8 Mark Salmon, 22 Darragh Noone; 7 Ryan Brennan , 11 Gary McCabe, 9 Aaron Greene ; 20 Anthony Flood