For so long it looked like Town would secure an elusive second away win of the season, only for West Ham United to complete a late second-half comeback to claim all three points on what was a dramatic afternoon at the London Stadium.
Twists and turns aplenty, it looked ominous as Mark Noble stroked home a penalty to give West Ham an early lead, only for Juninho Bacuna and Karlan Grant's first of the afternoon to send the Terriers in at the break ahead. Grant's beauty added a third, but it wasn't to last long thanks to Angelo Ogbonna and Chicharito's brace rounding off an eventful game to say the least.
Five changes were made to the Town starting XI, one of which being the full debut for young Londoner Aaron Rowe on the right-hand side, in for Elias Kachunga. In the defensive unit, Terence Kongolo returned ahead of Zanka, and Skipper Tommy Smith returned from a three-game suspension to replace Christopher Schindler, who missed the clash in the Capital through illness. Chris Löwe and Karlan Grant preferred to Philip Billing and Steve Mounié rounded off the alterations, with a positional shuffle slotting Juninho Bacuna into central midfield, not the full-back role he had occupied for weeks previous.
Town looked composed in possession to start proceedings, although it was the home side who mustered the first meaningful attempt. Michail Antonio looped a close-range header onto the cross-bar from newly called-up England international Declan Rice's flighted cross as a loose touch from Karlan Grant in his own area presented a generous opening.
The Hammers started to grow in confidence. A number of slick exchanges eventually resulted in Manuel Lanzini pulling free. The Argentine playmaker - a scorer in HD1 last season - looked to deliver a low cross for the cavalry of Arnautovic and Felipe Anderson only for a determined Aaron Mooy block to divert away.
Lanzini remained in the thick of the action, this time being brought down by full debutant Rowe inside the box to which referee Jonathan Moss awarded a penalty. Mark Noble duly converted to send Manuel Pellegrini's men a goal to the good; only for a matter of minutes, though.
Juninho Bacuna's first goal in Town colours brought the Club level, with the Dutchman taking advantage of some questionable West Ham defending to power home a thumping header into the bottom corner from Aaron Mooy's corner.
Like London buses, when one comes, so does another; and it stemmed from another set-piece situation. Karlan Grant utilised clever movement in the six-yard box to tuck home Chris Löwe's tantalising low cross, who initially received a pass in space down his native left thanks to Alex Pritchard's quick-thinking whilst the Hammers' defence slept once again.
The turnaround had deservedly been completed 10 minutes before the break. As the home crowd grew more and more anxious, both the travelling contingent from West Yorkshire and Jan Siewert would have been over the moon with just how events had unfolded in East London. Town was showing a clinical edge which hasn't been all too familiar throughout this campaign.
It may well have got even better for the men in blue and white. Grant had the freedom of the London Stadium to gallop forward and instigate a shooting chance, but a decent recovery from Issa Diop and Angelo Ogbonna cut short the two-on-two opportunity which concluded with Alex Pritchard stumbling on the ball.
On the other hand, United could well have equalised. Jon Gorenc Stanković's sensational sliding block denied Aaron Cresswell's surge having been found by Anderson's cross on a swift counter.
Inevitably, the Hammers were bound to apply pressure in a bid to begin their quest of a turnaround themselves. However, Town reasonably withstood marginal pressure, and produced a good chance to add a third. Łukasz Fabiański was at full stretch to thwart Juninho Bacuna from doubling his tally for the afternoon with a piledriver from distance.
The true Terrier was certainly back. Dogged and tenacious in every tackle, each and every player dug in. Ogbonna had to be alert to clear Tommy Smith's dangerous cross as Karlan Grant looked to double his own personal tally for the encounter.
Karlan wasn't able to on that occasion; but he certainly obliged in the follow-up in spectacular circumstances.
Having soaked up a tough period of pressure around the hour mark, the away end was sent into utter jubilation as their side were deadly on the counter. Terence Kongolo's inch-perfect threaded through ball into that man Grant saw the latter roll marker Ogbonna before superbly curling into the top corner.
It was a score-line that the Hammers were doing their utmost to recover from, albeit to no avail as Siewert's group had tirelessly gone about their business on a blustery day in the East end.
The two-goal cushion wouldn't be in place for long, as the Hammers responded to cut the arrears. Ogbonna made up for his misdemeanour in keeping Grant at bay to head home Aaron Cresswell's out-swinging corner having been unmarked on the penalty spot.
That momentum harnessed the equaliser. A deep cross from Pablo Zabaleta worked its way all the way through to half-time substitute Chicharito at the far post. The Mexican made no mistake from close range, stooping to guide the cross into the corner beyond the reach of Jonas Lössl, who despite being beat three times, had a relatively quiet afternoon whilst just claiming a number of high balls.
And as a pulsating clash drew to a close, Town had a glorious chance to snatch the points right at the death. Jason Puncheon somehow skied over from three yards after a goalmouth scramble ensued. The unlikely figure of Terence Kongolo forced a save, and as the rebound went goalwards, Puncheon couldn't find the desired touch to bag the winner; and how it would prove costly.
With Lössl wrong-footed, Chicharito flicked home a late, late winner to complete a heart-breaking scoreline reversal to end what was once looking to be a perfect afternoon all-round for Jan Siewert and his squad.
A fortnight's break is in the pipeline, with the next action coming at Crystal Palace at the end of March (30 March 2019, 3pm).
Jonas Lössl; Tommy Smith (c), Jon Gorenc Stanković, Terence Kongolo, Erik Durm; Alex Pritchard, Juninho Bacuna (Jason Puncheon, 66'), Aaron Mooy; Aaron Rowe (Philip Billing, 54'), Karlan Grant (Steve Mounié, 70'), Chris Löwe
Ben Hamer, Zanka, Florent Hadergjonaj, Matty Daly
WEST HAM UNITED (4-2-3-1)
Łukasz Fabiański; Aaron Cresswell, Angelo Ogbonna, Issa Diop, Pablo Zabaleta; Declan Rice, Mark Noble (c) (Samir Nasri, 58'); Felipe Anderson, Manuel Lanzini, Michail Antonio (Chicharito, 46'); Marko Arnautović (Lucas Pérez, 67')
Adrián, Arthur Masuaka, Fabián Balbuena, Robert Snodgrass