West Allotment Celtic came from three goals down to defeat Darlington RA in extra time and book their place in the Ernest Armstrong Memorial Cup final.
A positive result for Allotment had seemed a near impossibility as the Railwaymen struck three times in the opening 30 minutes to all but seal their progression.
However, the hosts struck back through Liam Hudson before half-time, then a David Dormand header and a Sean Reid penalty levelled the scores to take the semi-final tie to extra time.
And midway through the second additional period, Michael Bell struck what proved to be the winner, completing a remarkable comeback at Whitley Park.
The hosts could not have wished for a worse start as they fell behind after just three minutes.
A deep set-piece found Martin Butterworth at the back post, and although his volley was wayward, Allotment failed to clear their lines and RA captain Dale Elgie stroked home a more accurate volley of his own.
The in-form visitors soon doubled their lead against a ragged Allotment side.
Steve Allison had already been prevented from shooting by Bob Rodgerson once, but he got the better of the Celtic keeper the second time, winning a 50-50 challenge and side-footing into an empty net.
Sean Reid sliced a half-volley wide of goal in a rare Allotment attack, but Darlington were rarely troubled - and were soon gifted a third.
Butterworth latched onto Marc Allen’s wayward back pass and lashed a 20-yard effort in off the underside of the bar to give the away side a seemingly unassailable lead.
Lee Farrington almost capitalised on a similar mistake from Rodgerson, instead clipping the top of the bar.
But just when Celtic looked out of it, they clawed their way back into the game before the interval.
Some persistent pressure from Reid yielded possession in a dangerous area and the energetic midfielder found Hudson with a perfectly timed pass, and the forward stroked it into the bottom corner to give Allotment a modicum of hope at the interval.
Allotment started the second half brightly, with captain Ian Dunn entering the fray.
However, chances were few and far between until the introduction of Dormand.
The forward unsettled keeper Matt Calvert in the air and the ball ultimately broke to Hudson, whose effort clipped the outside of the post.
The substitute went one better four minutes later.
Chasing a Paul Stoneman long ball, Dormand beat the offside trap and powered a header from outside the box over the on-rushing Calvert to pull Allotment just one goal shy of the shell-shocked visitors.
Spurred on by the home support, Celtic poured forward in search of a third, penning Darlington back in their own half.
Calvert got down well to tip away a Reid free kick, but could only watch as one of his defenders brought down David Henderson in the area following a fine team move.
Reid slotted home the penalty to make it 3-3.
Both sides had chances to win it in regulation time, with Dormand seeing an effort cleared by a covering defender and John Pendlebury performing the same last-ditch action at the other end to prevent Steve Allison’s cross from finding its target.
However, neither side could add to their respective tally in the latter stages, taking the game to extra time.
Buoyed by their resurgence, Allotment took the game to Darlington.
Hudson fired one effort well wide and another straight at Calvert, whilst Reid awkwardly volleyed past the post from close range.
But their persistence finally paid off with ten minutes remaining.
Reid nodded a set-piece back into the six-yard box and Bell was there to sweep the ball home, sparking wild celebrations on and off the pitch.
There was still time for more drama as the heroic Stoneman threw himself between the ball and the back of the net, preventing the Railwaymen from taking the game to penalties.
Thereafter, Allotment ran down the clock and ultimately sealed one of the most astonishing wins of the season against a very strong Darlington RA side.
West Allotment remain on course to pick up their first piece of silverware since 2005, and will take on either Jarrow Roofing or Northallerton Town in what should be a similarly enthralling finale.