Neil Warnock's Huddersfield Town stunned Carlos Corberan's West Bromwich Albion with an injury-time winner as the Terriers gave the perfect response to last Saturday's 4-0 home battering by Norwich City.
Jack Rudoni struck in the 96th minute with a well-struck low, left-foot shot that sneaked inside the right post.
That earned the Terriers their first win of the season and it also put an end to Albion's 100% home start.
Huddersfield had taken the lead on 33 minutes with a goal from Delano Burgzorg on his full Terriers debut, only for John Swift to level on 52 minutes, with his third goal in successive home games this season.
But, just after Albion substitute Josh Maja had gone close to winning the game at one end, Huddersfield went down the other end and Rudoni kept his cool to complete a classic smash and grab against Corberan's old club.
In response to Huddersfield owner Kevin Nagle labelling last Saturday's 4-0 home defeat by Norwich City as "unacceptable", "disappointed" veteran Terriers boss Warnock made four alterations, as well as deploying a change of shape to 3-5-2.
On top of new midfield signing Ben Wiles making his debut following his arrival from Rotherham United, Burgzorg, David Kasumu and Jaheim Headley all came in for their first league starts of the season.
Having signed too late for new full-back Pipa to be included, and having perhaps more crucially not lost any more players during the summer months window, Albion's two changes were both at the back. One of them was forced, due to the absence of Semi Ajayi through illness - but it was further forward where the Baggies looked off-colour.
Other than a delightful Jed Wallace backheel and a clever Matt Phillips run and wickedly-deflected cross that almost opened the visiting defence, it led to a stifling of Albion's creative output.
And, on a day when the home fans led a loud, orchestrated show of collective disaffection towards the club's owners on 12 minutes, the players failed to match the supporters' spirit.
The Baggies' lack of spark was shown up when Huddersfield went ahead on 33 minutes. It was a decent enough strike by on-loan Spezia striker Burgzorg, but Albion keeper Alex Palmer might have been disappointed to be beaten at his near post.
Albion were behind until seven minutes into the second half when Swift kept up his happy habit this season of scoring in every home game.
Jayson Molumby's incisive pass sent Brandon Thomas-Asante away, the Albion striker had the presence of mind to spot Swift sprinting clear down the inside right channel in yards of space, squared to his right into Swift's path and the Albion midfielder ran on to fire home a powerful right-foot finish.
Neither side really created any clear-cut chances other than Yuta Nakayama's long ball finding fellow sub Kian Harratt, who could only find the side-netting from a narrow angle.
But, when Terriers keeper Lee Nicholls dived to his left to keep out Maja's shot, the visitors broke quickly down the right, Harratt worked the ball back to the unattended Rudoni and he pulled back the trigger to send the 855 away fans in the 23,094 crowd home happy.
Both sides now have a clear fortnight before their next game because of the September international break.
Albion will resume with an away trip to Bristol City, on Saturday, 16 September, when Huddersfield face a local derby at home to one of Warnock's many former clubs, Rotherham United.
West Bromwich Albion head coach Carlos Corberan:
"The Championship is a difficult competition. Conceding two goals is too much to win games in this league.
"In the first half our pressing was no good.
"In the second half, we had to change the shape to improve."
Huddersfield Town boss Neil Warnock told BBC Radio Leeds:
"We deserved it. We could have scored more, although Lee Nicholls made an important save just before we broke and scored the winner.
"It would have been a crime if we had got beaten. And, with Del [Delano Burgzorg] getting his first goal, it could not have worked out any better, especially going into a fortnight's break.
"Everybody was writing us off and saying we were favourites to get relegated.
"But there's no better feeling in football than the coach on the way back after a good away win like that."