SUPERSUB Tiarnan Mulvenna finally broke the resistance of a Shelbourne side in desperate need of points to lift them off the bottom of the table.
The visitors looked set to leave Oriel Park on Friday night with at least a point and thwart Dundalk from recording back-to-back wins at home for the first time since October 2010.
However, Mulvenna was introduced with just over half an hour left and netted the vital goal that Shelbourne had so resolutely denied them for 87 minutes.
Stephen Kenny made three changes in personnel from the starting line-up at Tallaght Stadium, with Dane Massey filling in for the injured Mark Rossiter beside Andy Boyle, while Vinny Faherty started in attack with Kurtis Byrne, as John Dillon, Faherty and Eoghan Osborne came into the team for Mountney, Darren Meenan and Patrick Hoban.
To their credit, before Mulvenna broke the deadlock so late in the game his colleagues had already worn down the Reds. They had to absorb virtually constant pressure in the second half after a dull opening 45 minutes when the Shelbourne gameplan of concentrated defence failed to see them create a single shot at goal, while Peter Cherrie made his first save after 75 minutes.
Their plan was undermined by the loss of their best player Brian Shortall, in which Mulvenna had an unwitting part, with the centre-half striking the substitute with a wild kick in the stomach and being shown an instant red card 12 minutes from time.
The strain of trying to hold out was already starting to tell at that stage and the livewire Mulvenna's speed and fresh legs helped stretch and pull defenders out of position to create gaps.
Ultimately, with a player short the visitors cracked, and captain Stephen O'Donnell was the shrewd architect of the winning goal with a brilliantly disguised pass into the penalty box to free Mulvenna who advanced to drill a shot low through the legs of Ger Hanley, one of a number of Shels players who formerly was at Oriel Park.
Dundalk should have have pocketed the points by then, with Dane Massey and O'Donnell failing to capitalise on two glorious goal chances in the opening five minutes of the second half.
Massey, completely free in front of goal, failed to make contact with his head to a swinging corner by John Dillon after 47 minutes.
A couple of minutes later the most clear-cut opening of the match fell to the captain 12 yards out. Hanley left his line to claim possession, but dropped the ball straight into O'Donnell's path. However, his shot hit the butt of the post with the goal wide open.
Vinny Faherty, who had a subdued game, headed unchallenged straight at Hanley on 59 minutes and when O'Donnell skimmed the bar with a vicious volley from the edge of the box six minutes from time the home side was facing a second scoreless draw of the season, with their opening game against Shamrock Rovers the only one of the campaign that didn't produce a goal.
But they could have added a couple of more goals in the dying minutes, with an audacious long-range shot by Richie Towell and a lofted effort that drifted just wide from Darren Meenan. That chance came after Hanley beat Mulvenna in a race for possession to the edge of his penalty box, only for the ball to break to the winger.
Shels had set out their stall from the start, placing their trust on defence and in a drab first half the sum total of five shots was recorded - all from Dundalk - with neither keeper required to make a save. Dundalk did once have the ball in the net, but Faherty was already signalled offside when he received the ball in the penalty box from O'Donnell.
It took 21 minutes for Dundalk to win a corner and that produced their first scoring attempt, with Andy Boyle powering a header at the back post over the bar from Dillon's kick.
Keith Ward, the side's most inventive player, cut in-field from outside the box on the left to make an opening to shoot beyond the far post four minutes later.
That was followed by Faherty's disallowed goal on the half-hour, before Dillon struck the best effort at breaking the deadlock from outside the box. It flew over the bar at the end of a concerted team move that started inside the home side's half when O'Donnell did well to keep the ball in play on the touchline.