South Africa defeated England by one run after an astonishing finish to the first T20 international at Buffalo Park.
Chasing 178, England looked poised for victory after Jason Roy scored a rapid 70 and captain Eoin Morgan added a vital 52 that included some clutch late boundaries.
The tourists only needed seven from the last seven balls but Morgan holed out to long on to set up a tense finale before a tremendous last over from Lungi Ngidi (3-30) saw him remove Tom Curran and Moeen Ali.
At eight down, Adil Rashid was left needing three from the final delivery for victory or two to force a super over, but he could only manage one as the returning Dale Steyn and captain Quinton de Kock combined for a runout that sparked joyous scenes in East London.
Earlier, South Africa were well set for a huge total before England recovered to limit them to 177-8.
Roy's superb innings – which saw him become the country's first player to score three consecutive T20I fifties - took just 38 balls with seven fours and three sixes as Morgan's men made a strong start to their reply.
Morgan appeared ready to put the finishing touches on a strong run chase but a dramatic conclusion meant it was South Africa who took a 1-0 lead in the three-match rubber, with their opponents finishing agonisingly short on 176-8.
England are now in danger of losing their first T20I series since July 2018 and this morale-denting defeat was an unwelcome start to a year that builds towards the T20 World Cup in October.
After being put in by England, the hosts got off to an electric start as De Kock scored a quickfire 31 off 15 balls, with Temba Bavuma keeping things moving as he put on 63 with Rassie van der Dussen.
South Africa looked poised for a huge total when they reached the halfway stage at 105-1, while England looked ragged after multiple mis-fields.
But Ben Stokes and Rashid accounted for Van der Dussen (31) and Bavuma (43) in consecutive overs and, despite some dropped catches, England's bowlers turned it around as they restricted the Proteas to just seven total boundaries in their last 10 overs.
After Steyn removed Jos Buttler to become the hosts' leading T20 wicket-taker, Roy smashed JJ Smuts for 22 runs in the fourth over as England set the tone for their reply.
They looked comfortable as Roy brought up his fifty in just 22 deliveries, putting on 72 with ODI opening partner Jonny Bairstow (23).
Morgan and Roy added 41 for the third wicket before the opener fell to a Beuran Hendricks slower ball.
England still looked comfortable, needing 46 runs from 34 balls, and although cheap dismissals for Joe Denly (3) and Stokes (4) meant things suddenly got tense, Morgan struck two fours and a six in the penultimate over.
But it went sour for England from there, as Morgan's dismissal to Hendricks gave Ngidi something to defend and the fast bowler delivered spectacularly.