Watford fought back from 2-0 down to defeat Wolves 3-2 and reach the FA Cup final.
With 11 minutes left, Wolves looked on course for their first FA Cup final since 1960 as they led through Matt Doherty's first-header and Raul Jimenez's superb chest down and volleyed finish.
Gerard Deulofeu was sent on to rescue Watford after that second goal and fulfilled his mission in spectacular style.
Deulofeu, however, was the catalyst and he showed composure and quality to provide the decisive contribution, steering a finish beyond John Ruddy in the 104th minute to send Watford to their first FA Cup final since 1984; they will meet Manchester City on 18 May.
Watford manager Javi Gracia said: "It was very tough. We started playing, working after [the FA Cup win over] Newcastle, after QPR, after Crystal Palace and now after Wolves. Everything was lost - we were able to show our character and at this moment I am very proud of my players.
"You always believe you can score one goal because in all the games this season we have always competed until the end. It wasn't different today. We tried until the end and sometimes it happens if you believe. Today we showed our strength as a squad, our belief. I am very proud."
Wolves manager Nuno Espirito Santo also told BBC Sport: "It was an emotional game. We had it, and it got away from us. It was a sad moment, we cannot hide it. Now it is disappointment and sadness.
"When it comes to four minutes of injury time, we should have possession of the ball. We couldn't handle that and we got punished. We are disappointed. This is football, we must stand again, we have things to fight for, but I am very proud.
"I honestly think we should have done better in the last moments of the game."