It looked a tall order for Brig after Shields took the lead midway through the first half through Jon Shaw, but two quickfire goals on the half hour mark from Adam Dodd and Adam Roscoe sent Brig in ahead at the break.
The visitors were level soon after the restart as Robert Briggs made it 2-2 from the spot, but a late goal from Kieran Charnock ensured Brig ran out winners in a thrilling game of football.
Brig midfielder Michael Potts had the first effort of the game, with a volleyed strike from the edge of the box that dipped over the crossbar.
But after 20 minutes of controlled possession, Shields took the lead when Jon Shaw sneaked in at the back post to head home from the corner.
Despite seeing precious little of the ball in the opening exchanges, Brig were gifted the chance to equalise when Julio Arca hacked down Regan Linney after a mazy run from the number-11.
Dodd stepped up and calmly slotted home the spot kick into the bottom right corner to level things up.
And as the saying goes, one brings two. Just two minutes after equalising, Alistair Waddecar delivered a beauty of a cross and Adam Roscoe was there to bullet the header into the roof of the net.
After that goal the Mariners rallied once again and took control of possession, but Brig remained dangerous on the counter attack.
Lloyd Rigby was called into action early in the first half and reacted superbly to tip Robert Briggs’ shot that was destined for the bottom corner, round the post.
Shields started the second half in similar fashion to the first and within five minutes of the restart they were handed the chance to equalise from the spot, when Matt Lawlor was penalised for a foul.
Up stepped Briggs and this time the No.8 did beat Rigby with a pinpoint penalty into the bottom right corner.
Once again, Neil Reynolds' side responded well and won a succession of corners after Danny Forbes and then Michael Potts saw their well struck efforts deflected behind.
The second half was evenly contested with neither side creating a great deal, whilst remaining solid at the back.
However, on the 80th minute the moment every Brig supporter was dreaming of arrived.
Connell produced an unbelievable save to keep out Roscoe’s header, but Charnock was on hand to turn the ball into the net after a goalmouth scramble in the Shield box.
That goal set up a nervy last ten minutes to say the least and as expected Graham Fenton and Lee Picton’s side came at Brig in hunt of a leveller.
But Brig stood firm, showing no intention of letting up their lead and they saw the game out admirably to earn arguably their biggest three points of the season.
It was 90 minutes that was a great advert for the league, as Brig continued their fine home form to inflict only South Shields’ third defeat of the season.