The Town threw away a 3-1 lead to lose 4-3 at Kenilworth Road as Carlisle completed an incredible second-half comeback.
An early Jack Marriott goal had the Hatters 1-0 up after four minutes but United levelled a minute before the break through Charlie Wyke’s strike.
But the Town seemed to be on their way to three points when Josh McQuoid and Danny Green struck to make it 3-1 before the hour mark.
However, the Cumbrians – the league’s leading goalscorers who also possessed the leakiest defence – turned the game on its head with three goals in an unbelievable 14 minutes to leave Kenilworth Road stunned.
Substitute Alex Gilliead made it 3-2 on 66 minutes before fellow substitute Jaho Ibehre brought United level on 79 minutes. Then, precisely one minute later, Derek Asamoah completed the turnaround to put the visitors 4-3 in front.
The Hatters, who were brimming with confidence at 3-1, struggled to find a leveller as time ticked down – Green came close with a long-range free-kick but, despite five added minutes, the Town couldn’t find a way through and Carlisle held onto celebrate an astonishing victory.
The final scoreline seemed a millions miles away from the minds of the Town after an hour gone with Marriott, McQuoid and Green’s efforts putting John Still’s side in command.
Marriott, in the starting XI for the suspended Paul Benson, opened the scoring after four minutes with a well-taken effort after being found by Olly Lee. It was the striker’s eighth goal of the season.
Gradually, the visitors worked their way back into the game and the Hatters had Mark Tyler to thank on the quarter-hour to keep out Jason Kennedy’s close-range shot.
United were having the better of the ball as the first half continued but the Town still created the better chances. Marriott rolled a left-foot shot across goal before finding the midriff of Carlisle keeper Mark Gillespie.
But the visitors kept chipping away at the Hatters’ defence and a simple long-ball led to their leveller a minute before the break. Wyke raced on the raking pass forward and coolly slotted past Tyler to make it 1-1.
However the Town needed just 50 seconds after the restart to restore their lead. Green was the creator, whipping in a perfect right-wing cross that McQuoid nodded home from inside the six-yard box for his fourth of the campaign.
Back in front, the Hatters’ early second half verve continued and Green gave the Town a two-goal cushion with another fine goal on 57 minutes to make it 3-1. His free-kick from the edge of the penalty area was blocked by the United wall but the winger received the ball back and looped a fine finish high into the top corner giving Gillespie no chance.
With Kenilworth Road enjoying the Town’s confident football – oles could be heard after one passing passage – what happened next simply left the stadium shell-shocked.
Carlisle’s comeback began on 66 minutes when substitute Gilliead finished well after receiving Wyke’s knock-down and all of a sudden the visitors smelt blood.
United thought they levelled on 72 minutes when Ibehre slid the ball home after Tyler had spilled a long-range effort from Danny Grainger only to see the goal chalked off for offside…but the Town weren’t so lucky on 79 minutes when Ibehre hooked home a shot into the bottom corner following a right-wing cross to make it three apiece.
But worse was to follow for the Town exactly 60 seconds later when Carlisle went in front for the first time. Asamoah picked up the ball on the left flank and ran with the ball to the edge of the area before letting fly with a low shot that crept agonisingly past Tyler.
It was hard to take it all in as the Hatters had gone from leading 3-2 to trailing 4-3 in the space of a minute.
Asamoah threatened a fifth for United on 88 minutes but, as the Town pushed for an equaliser, the closest they came to finding one came when Green’s low free-kick from fully 35 yards was turned behind by Gillespie.
And that was that. The Hatters faced up to the reality of letting a two-goal lead slip for the third time this season to lose in quite extraordinary fashion.
Town: Tyler; Lawless, Griffiths, O'Brien, Cuthbert; Smith, Lee, McGeehan (sub McCourt 82), Green; McQuoid, Marriott (sub Mackail-Smith 70).
Subs not used: Hall, Williams, Doyle, Justham.
Attendance: 7,298, including 169 from Carlisle.