Ali Crawford was the last minute hero to dramatically lift St Johnstone off the foot of the table.
A terrific start from the Perth side was rewarded when towering striker Callum Hendry superbly nodded beyond helpless Max Stryjek.
But Saints weren’t able to take further advantage while on top and Bruce Anderson levelled proceedings before the break.
It looked certain to be a point apiece but with the final whistle just seconds away, up stepped Crawford to lash home the winner. The travelling support erupted, with many spilling onto the pitch in celebration - and relief.
Eight new faces - outwith loan recalls - have arrived across the past few weeks to aid Saints’ push for Premiership safety.
But boss Davidson largely put trust in familiar faces for what was another huge evening of football at the Tony Macaroni Arena.
Melker Hallberg did get the nod from the start in the centre of the park and he was one of three changes from the Dundee stalemate.
Also returning from the off were Crawford and Stevie May while, dropping to the bench, were Murray Davidson, Nadir Ciftci and Cammy MacPherson - the latter two absent completely.
Deadline day signings Tom Sang and Jahmal Hector-Ingram had to settle for a spot on the bench, as did John Mahon and Tony Gallacher.
To point out the blindingly obvious, Saints were crying out for goals having, before kick-off, netted just 11 in 23 league matches.
Experienced forward May attempted to carve out a quick start when he raced towards goal from distance in the opening minutes.
But he was charged down by defender Ayo Obileye and the chance was gone.
Saints, clearly, were really up for this and the pressing game that was so often successful last term had made a return.
Hallberg was soon earning the applause of the travelling support with a number of neat touches and a clever range of passing.
He helped kick-start a neat Perth move in the 11th minute where the ball was eventually worked right to advanced Cleary.
The Irish defender clipped a beautiful cross into the box and there was Hendry, up like the finest of Perthshire salmon, to nod a terrific header into the bottom corner.
Livingston had looked shaky and continued to do so after the opener, much to the annoyance of home fans. But they were up cheering a leveller on 34 minutes.
Alan Forrest, the subject of recent interest from McDiarmid Park, navigated to the byline and crossed for Anderson to tuck into the net from close range.
Saints would be kicking themselves as the teams wandered in for a quick break but there was still plenty to play for in the second half.
Hendry looked to fire the Perth side back in front not long after the restart with a powerful drive from the edge of the box. The ball, however, was always rising.
Up the other end, Forrest was continuing to be a menace and he twice went close around the hour mark. First he twisted inside the box and sent a deflected effort inches wide of the post.
Then he sized up a free-kick and, although his fine curling attempt was on target, big Zander Clark was over quickly to tip behind for a corner. A very smart stop.
Perth captain Liam Gordon was soon needing replaced and that paved the way for Mahon, recently signed from Sligo Rovers, to make his debut.
On 67 minutes it was Cleary embarking on a weaving run down the left flank, superbly working space for a clipped cross into a dangerous area. There were no takers.
Hallberg’s evening was then up - he could be happy with his first appearance - with Davidson the replacement.
It appeared to be heading for a point apiece but substitute Glenn Middleton, in stoppage time, worked to the byline and crossed into the box.
The ball broke for Crawford and he slammed home to clinch the most dramatic of victories. Relief poured out from the away support who clambered onto the pitch in celebration.
