gap Connah's Quay Nomads were dealt a demoralising blow in their bid for the league title when Darren Thomas netted an injury time free kick to hand Llangefni the spoils in a thrilling encounter at the Deeside Stadium.
Gary O'Toole looked to have salvaged a draw with his fourth hat-trick of an incredible scoring season, after the visitors had taken a three-goal lead inside 33 minutes to stun Mark McGregor's side.
But Thomas was on hand to deflate the jubilant Nomads when he struck a sweet, curling effort inside Louis Mackin's near post in the third minute of added time.
McGregor made one change to the side that ground out a narrow victory at Caersws seven days previously, with the injured Rob Jones making way for Dean Thurston, as Stuart Scheuber returned to the side on the bench.
Nomads took advantage of the continuity offered to them through a now firmly settled line-up and started strongly with Ben Collins and Alan Hooley marauding down the left flank - both seeing low crosses well bloked by veteran visiting stopper Mike Innes.
Soon after, the unmarked James McIntosh should have done better when he hooked a shot over from Thurston's mis-kick, but his blushes were spared by an offside flag.
Comfortable in possession during the opening exchanges, the hosts looked to take the game to their opponents, but the defending champions responded in a vengeful manner - attempting to erase the memories of Michael Hayes' four-goal haul in a 5-1 Nomads rout prior to Christmas.
After Louis Mackin had made a smart save to deny Darren Thomas' powerful header, and Rob Marshall-Jones had sent a header from a corner flying over the bar, the visitors took a 17th minute lead through midfielder Tom Dix.
Kevin Roberts found room on the edge of the Nomads penalty box to slam a shot goalwards, which Mackin could only parry to the lurking Dix who poked home from close range.
By this point, player-boss McGregor had already been forced into replacing himself through injury as Ben Alston entered the fray in his place.
Nomads responded to falling behind by pressing forward but wasted a gilt-edged chance when Jamie Petrie's low shot was somehow diverted behind following O'Toole's powerful run and neat cut-back from the right side of the area.
McGregor's earlier withdrawal, though, unsettled the home defence and when Ben Alston and Tommy Baker made a hash of a clearance midway through the half they should have been punished, but Lee Craven blazed high and wide when well placed to score.
With the Nomads backline looking decidedly shaky it came as no surprise that the visitors doubled their advantage on the half hour.
After a Nomads corner came to nothing 'Cefni broke forward on the counter with Evans' long crossfield pass picking out Thomas who outmuscled makeshift centre back Baker to fire through Mackin's legs.
Just three minutes later, Nomads were reeling once more when Evans raced through to beat Baker to a long ball before stepping inside and slotting in-between Mackin and his near post from all of six yards.
McGregor immediately sought to make amends by sending fit-again Danny Forde into the fray in place of McIntosh - bringing about a switch in formation to 4-4-2 - and three minutes before the break Nomads were handed a lifeline when O'Toole raced clear of a static visiting defence on the left to curl into the bottom far corner.
Trailing 3-1 at half time, the hosts had to be quick out of the blocks in the second half and after a cagey quarter of an hour, three chances came Nomads' way in quick succession.
First, Collins blazed high and wide when well placed after meeting a neat Thurston pass before Thurston himself cracked a first-time shot on the run straight at Innes following Petrie's dangerous run and cross.
O'Toole was next to try his luck, lobbing a 25-yard effort narrowly over after Innes had hurried his clearance.
With less than 15 minutes remaining the home side's pressure was rewarded when O'Toole notched his second of the match - charging through the centre of the 'Cefni defence and smashing a powerful shot into the corner of the net.
Nomads' tails were up and they surged forward in a bid to complete a remarkable turn-around, missing an array of gilt-edged chances in the process.
Substitute Sam McNutt floated a free kick towards the towering Andy Alston at the far post and his cushioned header across the goal was agonisingly flicked wide by O'Toole - missing Thurston on the post.
There was more disbelief to come for the home support when Hooley's delightful pass released Collins on the left flank but his cross into a crowded area was directed to the on-rushing O'Toole who somehow failed to connect with the ball inside the six yard box.
With five minutes left on the clock the onslaught was finally rewarded when O'Toole broke through to plunder his 30th goal of the season, completing his hat-trick to send the home side into wild scenes of celebration.
Nomads continued to push forward in search of a winning goal - something which seemed improbable during the first half - and Thurston was guilty of shooting straight at Innes after meeting Collins' testing left-wing cross at the near post.
With the final whistle fast approaching the visitors were awarded a free kick on the left side of the area in the 93rd minute after a foul on Thomas. The highly-rated striker duly despatched his effort around the wall and beyond Mackin's dive to turn Nomads' delight into sheer despair.
All eyes are now focused firmly on Belle Vue where Nomads take on the new league leaders Rhyl for a joint-top tussle on Tuesday evening with the title now in the balance.
NOMADS: Louis Mackin, Tom Baker, Ben Collins, Mark McGregor (Ben Alston 13'), Andy Alston, Craig Jones, Jamie Petrie (Sam McNutt 75'), Alan Hooley, Gary O'Toole, James McIntosh (Danny Forde 33'), Dean Thurston.
Substitutes not used: Stuart Scheuber, George Baxter.
Booked: Danny Forde, Craig Jones.