Around 3,000 Swindon fans made the trip to South East London for the biggest game of the season for Swindon.
The game got off to a bad start for Swindon with David Lucas going off injured aftre only one minute of play. He was replaced by Phil Smith.
An own goal by Simon Ferry gave Charlton the lead on the night on 27 minutes.
Shortly before half time Charlton scored again to make it 2-0 on the night, and 3-2 overall. The Charlton goal was scored by Mooney.
Swindon looked alot better in the second half, and it looked like it would only be a matter of time before they scored. Things then started to look less likely when on 67 minutes Greer was shown a straight red card.
However by 74 minutes Danny Ward put Swindon back in the game from close range making it 3-3 overall.
Swindon pushed forward for a winner in normal time, and nearly got it. Charlton were themselves reduced to ten men late on when Llera was sent off, but Swindon wasted the free kick.
After 30 minutes of extra time was played, a penalty shoot out had to take place.
Charlton took the first kick, and scored, then missed their second, before scoring the rest. Swindon this time managed to score all 5 penalties, with Darby scoring the final important kick for Swindon taking them to Wembley.