MK Dons were left to lament the substitute appearance of Carlisle United's Jordan Cook who came off the bench to score twice, including the decisive second from the penalty spot, to come from behind and send Karl Robinson's men to a 2-1 defeat.
After Lee Miller missed a second-half penalty the Dons took the lead through their own spot-kick when Shaun Williams converted with ease. But Carlisle quickly found a way back through Cook and when Tom Flanagan tripped him in the 90th minute the Sunderland loanee added to the Dons' woes with a successful penalty.
It will be a tough defeat to take for the Dons, only their third at stadiummk in the League, because they had a Luke Chadwick effort ruled out when the home side felt the ball had crossed the line. They also had a goal from Dean Bowditch disallowed for an offside decision.
Top goal scorer Bowditch returned to the fold so too did Luke Chadwick as Karl Robinson opted to ease the strain that Alan Smith and Jay O'Shea have both endured of late by naming them on the bench ahead of a busy run-in.
It was a lively start at stadiummk helped by the set-up of Carlisle who, with their own play-off ambitions, showed signs of attacking football rather than the defensive style often enforced by visiting teams to MK1.
Both sides were in an energetic mood but it wasn't until the 11th minute when Mathias Kouo-Doumbe picked up the ball on the right and fizzed a fierce left-footed shot inches over, that a clear attempt on goal was registered.
Soon after Charlie MacDonald called the Cumbrians' 'keeper Adam Collin into action when he broke down the left of the box but was forced into an acute angle when he shot at the goalie.
Former-Dons Jon-Paul McGovern causes some problems with his trademark tricky down the wing and when he turned a fine cross into the box Liam Noble, tracked all the way by Tom Flanagan, was inches away from connecting in the six-yard box.
A short spate of dead-ball chance came to Carlisle - a huge strength of the visitors - luckily for the Dons the chance had been few and far between, but the Dons had to sharpen up to avoid giving their guests he upper-hand.
When the Dons earned their own corner Dean Lewington's delivery was finding its way to Kouo-Doumbe, but the defender's marker got their first and caused a panic for his own goal as he nodded over the bar.
Carlisle showed why they were unbeaten in five with some fluid football on the counterattack. With great patience Greg Abbott's side soaked up pressure before hitting on the break and most of their positive play was found through their right channel with McGovern keeping his former teammate Dean Lewington on his toes.
The Cumbrians' skipper Danny Livesey put himself in a dangerous position when he halted the run of MacDonald at goal, but received a caution for his cynical foul. In the meantime, Stephen Gleeson appeared to be struck around the back of the head by a Carlisle player in the aftermath of the foul on MacDonald yet it went unnoticed by the officials.
The first half fizzled out but the opening of the second half had plenty of drama when MacDonald and Powell combined to carve a route through to goal for Luke Chadwick. The midfielder steered the ball goal-bound and it appeared to cross the line before Peter Murphy dug out the clearance. However, assistant referee Alexandra Ihringova ruled otherwise and as a result the score remained goalless.
The Dons had more impetus in their forward play and some intricate work on the edge of the box almost created the opening goal when Powell fired a low effort from the right and he was only denied by a fine fingertip save from Collin.
Just 10 minutes after the interval Carlisle opted for a double substitution with Tom Taiwo and Francois Zoko making way for Jordan Cook and Andrew Walsh.
Meanwhile, the Dons were carving opening but found Carlisle a tough nut to crack with Livesey ever-present in defence. When Gleeson lofted a brilliant ball over the defence he released Bowditch into the box, the forward nodded the ball down to gain control but as he get beyond Collin, Livesey arrived to clear the lines.
Dons were dealt a blow when Kouo-Doumbe went to challenge Collin for the ball yet fell heavily and after trying to shake off the pain he was subbed for Jay O'Shea. It meant reshuffle in defence as Chadwick dropped back to right-back to make room for O'Shea.
Within minutes O'Shea's fast feet troubled the Cumbrians and Livesey's trip on the Irishman on the edge of the box present him with a shot at goal, but the midfielder's effort was always rising.
Despite being on top, the Dons were up against in the 73rd minute when referee Mark Heywood pointed to the spot for a handball in a crowded box against the home side. Striker Miller stepped up for Carlisle only to sky his shot high into the stands.
At the other end of the pitch Dons had an effort ruled out when Ibehre kept in a parried shot from O'Shea but strayed offside before passing to Bowditch who tucked home only for it to be cancelled by the assistant's flag.
The bit of luck the Dons had been looking for came on the 78th minute when Bowditch's legs were taken from under him and this time it was Robinson's men who were awarded the penalty. Williams took the responsibilities and placed a fine spot-kick to the goalie's right to fire the Dons in front.
However, celebrations were short-lived as Carlisle showed the desire that hand hinted all night and Miller made amends for his missed penalty to provide a cross from the left flank into the box for Cook who calmly slotted past Martin.
The further blow came when, in the 90th minutes, Flanagan was penalised for a trip on Cook just inside the box and they were awarded a second penalty. This time it was Cook who took the responsibilities and blasted into the bottom corner to ensure the visitors claimed all three points.
MK Dons (4-2-3-1): Martin; Kouo-Doumbe (O'Shea 68), Williams, Flanagan, Lewington (c); Potter, Gleeson; Powell, Chadwick (Smith 75), Bowditch; MacDonald (Ibehre 69).
Subs not used: McLoughlin, Hall.
Goal: Williams (pen) 79
Carlisle United (4-4-2): Collin; Simek, Livesey (c), Murphy, Chantler; Noble, Taiwo (Welsh 58), Berrett, McGovern; Zoko (Cook 58), Miller.
Subs not used: Gillespie, Madden, Michalik.
Goals: Cook 83, (pen) 90
Referee: Mark Heywood (West Yorkshire)
Attendance: 8,608 (594 away)
Goal-Don Goal times: 1st goal 78.58; 2nd goal 82.36; 3rd goal 90.00