Watford scored twice in added time to bring 10-man Birmingham's unbeaten league start to an end with a 2-0 victory at Vicarage Road.
The Blues looked nailed on for a point even though they had lost left-back Lee Buchanan to a second yellow two minutes from time.
That was for a foul on Yaser Asprilla and the sub took his revenge seconds into stoppage time when the Colombian crossed from the right and new boy Mileta Rajovic headed in to break the deadlock with Watford's first goal in three home games.
- Championship fixtures | table | highlights
- Stream the Championship and more with NOW
- Get Sky Sports | Download the Sky Sports App
There was worse to come for Birmingham as another sub, Ryan Andrews, blasted a second with 95 minutes and 28 seconds on the clock.
The visitors had started brightly, threatening inside the first minute when Oliver Burke's pass from the right set up Fulham loanee Jay Stansfield for a low right-foot shot from outside the box only for Hornets goalkeeper Daniel Bachmann to save.
Watford responded with a break down the left and, with just four minutes on the clock, City right-back Cody Drameh was booked for flooring Matheus Martins.
The Brazilian's free-kick was on its way into the net before Blues keeper John Ruddy stretched all of his 6ft 3in frame to stop the ball squeezing under the bar.
There was more early drama as Watford's Scotland defender Ryan Porteous fired a cross-shot from the right of the box against the far post in the ninth minute.
The Blues heeded that warning to employ a high press to keep the home side at bay. It worked, with Watford struggling to put together fluent moves - even from deep inside their own half.
Just after the half-hour, Watford's Tom Dele-Bashiru attempted to break the deadlock, surging through midfield before unleashing a shot that flew just over the bar.
Birmingham, managed by former Watford skipper John Eustace, were clearly determined to keep a clean sheet at all costs and two men were booked within three minutes of each other - Buchanan in the 35th minute for flooring Dele-Bashiru and then Krystian Bielik for a foul on Imran Louza.
The first half had been a hard slog for Watford - 70 per cent possession yielded just four shots, one on target.
Home fans were also concerned recently-signed striker Rajovic, a 6ft 3in target man, was getting very little service.
The Dane scored twice on his first start in Watford's previous match, a 3-3 draw at Coventry.
Two minutes before the hour, Stansfield went close for City with a shot that Bachmann just about kept out with a flying one-handed save to his left.
The Birmingham booking count had climbed to five early in the second half as first Stansfield, for heaving Porteous to the ground, and then midfielder Ivan Sunjic went into ref Keith Stroud's book.
Eustace also saw yellow but Birmingham sensed they could steal the points, Bachmann keeping them out with a double save from Scott Hogan nine minutes from the end.
Then the roof fell in on the Blues as Rajovic and Andrews struck dramatic late blows.
The managers
Watford's Valerien Ismael:
"I think that if we have a review of the first five games we should have more points but we made a lot of mistakes.
"Today was important for the mental side that we finally got the reward. We forced the red card and we forced the goals. Hopefully that will give the confidence to our players for the next game."
Birmingham's John Eustace:
"To come away with no points is really frustrating.
"I was disappointed with the inconsistency of the referee but it is what it is. No excuses, I still expect us to defend properly with 10 men, like we did with 11.
"They managed the game very well without getting punished.
"I was really pleased with the performance and I was very proud of the efforts of the group."