SHELL-SHOCKED Town were dumped off the top in their second worst defeat ever at the stadium.
It was supposed to be Town's night to celebrate the League I leadership and Peter Jackson's Manager of the Month Award in style, but Scunthorpe had clearly not read the script.
Lifted by Peter Beagrie's early penalty from a shocking decision by abysmal referee Carl Boyeson, Brian Laws' side powered to the top themselves on the back of an Andy Keogh double and Matt Sparrow's cleverly-placed header.
It was hard to stomach for Town - who replied through a Pawel Abbott penalty to briefly lift hopes - and only Port Vale's 4-0 win on the final day of the `Great Escape' season ranks worse since the Galpharm (formerly the McAlpine) flung open its doors in 1994.
Scunthorpe, to be fair, thoroughly deserved their first win in Huddersfield for 43 years, even though Town had the bulk of possession and very little luck.
The visitors kept two tight banks of four defensively and then terrified Town on the break with the pace of Keogh and Billy Sharp frightening when allied to the trickery of wingman Cleveland Taylor.
Not only that, but every time Town got possession they were closed down quickly in every area of the pitch.
It was a tactic which forced mistakes in the normally smooth attacking formula which Town adopt at home and, as a result, they struggled to get the dangerous Danny Schofield into the fray.
There was plenty of hard graft and some attractive sequences of passing, but Jackson's side just couldn't find their cutting edge in front of a crowd of 14,112 including 1,568 delighted followers from Glanford Park.
You got the impression it wasn't going to be Town's night from the moment Boyeson pointed to the spot when Paul Rachubka slid out to push the ball away from Sharp with only five minutes and 33 seconds on the clock.
It just didn't look like a penalty (a view supported by the video evidence) but Boyeson stuck by his decision after consulting the nearest assistant, who also had a nightmare match.
Beagrie's successful kick was followed by numerous bad decisions which infuriated Town and their fans and Scunthorpe's neat play on the counter attack did little to lessen the blood pressure.
Sharp saw one effort blocked superbly by Jon Worthington and another flash across the face of goal, but it seemed Town would go into the break just 1-0 down and with a chance to regroup for the second half.
Unfortunately, in the second of three minutes of added time, Tom Clarke made a hash of a half-volleyed clearance and Keogh burst away to double the Scunthorpe advantage.
It was clear Town would need to hit back quickly in the second half and they had the perfect opportunity when Paul Musselwhite - one of several players to slip quite often on the wet surface - spilled a low drive from Abbott to leave Gary Taylor-Fletcher with the goal at his mercy.
The hat trick hero from the Carling Cup, however, fired the rebound over the bar when it was easier to score and it took Town another 18 minutes to finally make that vital breakthrough.
Abbott's penalty came on 65 minutes when Chris Brandon was tripped by Richard Ryan - the striker sent Musselwhite the wrong way for his seventh goal in eight matches this season - and hopes were raised for a fightback.
Adventurous down the right, Andy Holdsworth, particularly, caused problems for Laws' men as the Galpharm crowd roared for an equaliser, but unlike the last time they came to this corner of West Yorkshire, it was Scunthorpe who provided the sting in the tail.
Substitute Sparrow got the killer goal on 73 minutes, nodding home from 12 yards after Taylor's drive had bounced down off the bar.
Then, after Worthington and Holdsworth had been denied at the other end, Keogh wrapped things up from Sharp's break with Town again badly shaken.
It was a painful lesson for Town after a magnificent run of results - they've lost just twice in 17 matches since March and not once at the Galpharm since December - and now would be a great time to start another long unbeaten sequence.