It was a wild finish deserving of the grandeur of the SCG in retro round, with Souths pulling off a daring 26-24 win in the dying moments.
While the Rabbitohs were playing for pride, tonight's shock loss catapults the Dragons into dangerous territory.
If the Panthers beat the Tigers on Sunday, for the first time all year the Dragons will be out of the top eight.
"That was a strange game - talk about momentum swings," Triple M's Ryan Girdler said.
"South Sydney tonight attacked a lot better than I've seen them do in a long time.
"Johnston played really well tonight, and John Sutton's combination with Cody Walker...they were crisp.
"The lead runners always looked like they were going to get the football and they pulled the Dragons defence apart when it counted."
There was a pressure kick for Reynolds to nab the win, with the Rabbitohs halfback his usual composed self and managing to knock it over from the sideline.
"A lot of practice pays off. It's a lesson for anyone out there, all the extra hours pay off," Adam Reynolds told the Triple M call team.
"It's still a pretty poor season, but it's a win tonight for all our members and fans."