•The night had begun well for Tottenham when Lucas Moura played a clever pass to Pierre-Emile Hojbjerg and his low cross, aimed at Son, was intercepted by Saints defender Jan Bednarek who could only turn the ball into his own goal.
•As the rain fell in north London there was still time for more drama as Tottenham substitute Steven Bergwijn thought he had rescued a point, but his effort was ruled out for a clear offside after a VAR check.
Southampton twice came from a goal behind to put a huge dent in Tottenham Hotspur's top-four ambitions with a 3-2 away win in a compelling Premier League clash on Wednesday.
Son Heung-min appeared to have secured a vital win for a ragged Tottenham with a superb finish 20 minutes from time.
But Southampton, who had been the better team throughout, struck twice in the space of three minutes.
Mohamed Elyounoussi headed in the equaliser before Che Adams won it for the visitors with another header -- James Ward-Prowse providing the crosses for both goals.
As the rain fell in north London there was still time for more drama as Tottenham substitute Steven Bergwijn thought he had rescued a point, but his effort was ruled out for a clear offside after a VAR check.
Tottenham's second successive league defeat left them in seventh place with 36 points, four points behind West Ham United albeit having played three fewer games. Southampton are 10th.
It was a stressful night for Tottenham manager Antonio Conte who watched his team get outplayed at times and defend appallingly. He also got embroiled in a fierce slanging match with Southampton players and technical staff after Son's goal.
"In the first half we made many mistakes and many times the pass was not good and we risked complicating our life today," Conte said. "The players gave everything tonight and that is why it was a pity to lose the game."
The night had begun well for Tottenham when Lucas Moura played a clever pass to Pierre-Emile Hojbjerg and his low cross, aimed at Son, was intercepted by Saints defender Jan Bednarek who could only turn the ball into his own goal.
Southampton immediately changed gear and begun to carve open a Tottenham side with some fluent football.
They drew level five minutes later when Tottenham failed to clear the ball from their area after Ben Davies had initially made a mistake and when Romain Perraud played the ball in Armando Broja produced a first-time finish.
Sensing Tottenham's unease, Southampton piled forward before halftime and Stuart Armstrong's header forced a fine save by Hugo Lloris. Perraud then let fly with a 30-metre thunderbolt that beat Lloris but cannoned off the crossbar.
Tottenham were still struggling to gain any sort of control in the second half and former Southampton player Hojbjerg made way for new signing Rodrigo Bentancur.
The hosts then took the lead in the 70th minute when Harry Kane played in Moura who whipped in a low delivery for Son to meet with a brilliantly-controlled shot.
Southampton felt there had been a foul on Broja by Emerson Royal in the build-up and while he was down having treatment, Conte lost his temper, gesticulating at Southampton players.
When order was restored it was Southampton who had the clearer heads and thanks to a couple of majestic Ward-Prowse crosses and some non-existent Tottenham marking they returned home with a deserved three points.
"The mentality and character of the team is outrageous, it is fantastic to watch," manager Ralph Hasenhuttl said.
"They are fighting for everything. We played fantastic football and played 23 passes before the second goal. Fantastic."