Substitute Edin Dzeko scored two late goals to earn 10-man Manchester City an unlikely win against West Brom.
The Premier League champions were facing an uphill struggle after James Milner's early red card for bringing down Shane Long when through on goal.
And City were staring at the prospect of a first league defeat of the season when Long gave the hosts the lead.
But Dzeko levelled with a header from a free-kick before finishing a blistering counter-attack in stoppage time.
If there was any question of City's championship credentials following three draws in their first seven matches of the season, they were convincingly crushed in the space of 10 second-half minutes at The Hawthorns.
While defeat was harsh on the Baggies, who almost snatched victory themselves when Joe Hart tipped over Romelu Lukaku's overhead kick just seconds before Dzeko's winner, this result had the mark of champions.
Roberto Mancini's men are quickly becoming the Premier League's comeback kings, and the man responsible is 26-year-old Bosnian striker Dzeko.
Signed for £27m from Wolfsburg in January 2011, Dzeko started City's incredible rally on the final day of last season when he scored in stoppage time to draw City level with Queens Park Rangers, shortly before Sergio Aguero's last-gasp winner clinched a dramatic title for the Blues.
However, before his latest intervention, City looked destined for defeat on what appeared to becoming a frustrating afternoon in the Midlands.
In fact they were lucky not to be reduced to nine men in a stormy first half in which Milner was sent off and Mario Balotelli cautioned.
England international Milner had no complaints about his dismissal for bringing down Long following a mistake in midfield by Vincent Kompany and a glorious throughball by James Morrison.
And Italian striker Balotelli was pushing his luck as, after being booked for a petulant foul on Claudio Yacob, he clattered into another Baggies player and was pulled away from the referee by team-mates as he uttered some choice words in the direction of referee Mark Clattenburg.
When Balotelli did calm himself down, he almost broke the deadlock with a moment of magic which took out two defenders on the left before his shot was well saved by Ben Foster. Carlos Tevez also went close in the first half as City looked to defy the loss of Milner.
The visitors continued to go close after the break, with Tevez having a shot tipped wide before Yaya Toure headed over from six yards out.
However, the spirited Baggies continued to impress when in possession and they took the lead when Peter Odemwingie's inch-perfect pass split the City defence and Long turned Joleon Lescott before calmly slotting past Hart.
It was the reward for some composed football, as the Baggies constantly probed with searching balls through the middle which eventually opened up the Blues.
City needed a reaction, as Baggies fans started to dream of their fifth home victory of the season, and they got it when Dzeko climbed highest to head past Foster in the 80th minute.
West Brom, however, showed resolve of their own and Lukaku had two good chances to seal victory for his side when he headed straight at Hart from six yards out before seeing his acrobatic shot tipped over by the England goalkeeper.
That proved to be decisive as City hit the Baggies on the counter, with Aguero squaring for Dzeko to stroke the ball home from the edge of the area and complete the comeback.
West Brom head coach Steve Clarke:
"I thought we deserved something out of the game. I thought we played well, stood up to Manchester City, but they showed when they went to 10 men that they are champions for a reason.
"Credit to them, their performance with 10 men was excellent and the only feeling I have now is being disappointed to lose the game so late.
"It was maybe a bad decision to go chasing the winner rather than settling for a point.
Manchester City assistant manager David Platt:
"If you look at Edin's career for Manchester City, the goals he has scored, he has got a lot of heavy goals, goals that are very important.
"I remember goals at Blackburn the season before last which more or less gave us Champions League qualification.
"You look back at last season as well and he got some vital goals. To win the league, Aguero's goal will always be the one but remember Edin equalised.
"He has been a threat all season and his form has been very good all season."