Wing Emiliano Boffelli touched down with the clock in the red as Argentina claimed a stunning 34-31 triumph over Scotland.
Gregor Townsend’s men were the better team for the majority of the first half, despite only going into the break with a one-point buffer.
Duhan van der Merwe and Ewan Ashman both touched down to give them a 14-13 advantage at the break, with Santiago Carreras’ try and two Boffelli penalties providing the hosts’ response.
Scotland then started the second period brightly and appeared to have put the match out of Argentina’s reach when Ashman and Van der Merwe crossed the whitewash once again.
Los Pumas had other ideas, however, and after Nahuel Tetaz Chaparro and Gonzalo Bertranou had brought them back into contention, Boffelli went over late on to complete a superb comeback.
Scotland had made eight changes following their second-Test victory with full-back Ollie Smith making his debut, and they came to life in the 13th minute.
Blair Kinghorn squeezed through two opponents and offloaded to Van der Merwe to power over the line.
Boffelli was soon involved as Argentina responded. The 27-year-old set up Carreras to go over and then kicked the hosts 10-7 in front.
The action continued as Ashman powered over after a lineout maul and Kinghorn added his second conversion.
Boffelli reduced the arrears with a penalty and Kinghorn hit the bar with a long-range penalty attempt in the final minute of the half.
Scotland took control in the opening 10 minutes of the second period.
Ali Price fed Kinghorn, whose quick pass allowed Ashman to cross out wide.
Van der Merwe then cut inside to follow up some good ball-carrying from his forwards to go over again. Kinghorn’s kicking put Scotland seemingly well in command, but the hosts hit back inside three minutes.
A needless penalty allowed Argentina to put the Scots under pressure and Tetaz Chaparro went over after the five-metre scrum.
Scotland’s pack helped them settle and Kinghorn kicked the visitors 11 points in front with 15 minutes left.
Argentina refused to buckle and Bertranou scored from close range in the 67th minute.
With Scotland four points in front, they passed up the chance to kick a penalty and Jonny Gray was held up as he forced his way over the line following the lineout.
Dave Cherry put in some big hits and Price produced a try-saving tackle as Scotland tried to withstand the pressure, but Boffelli had the final say when he dived over and then added a final flourish by kicking from the touchline.
Santiago Carreras (20′), Nahuel Tetaz Chaparro (51′), Gonzalo Bertranou (67′), Emiliano Boffelli (80′)
Emiliano Boffelli (21′)(53′)(68′)(80′)
Emiliano Boffelli (11′)(35′)
Duhan van der Merwe (13′)(49′) , Ewan Ashman (25′)(43′)
Blair Kinghorn (14′)(27′)(45′)(50′)
Blair Kinghorn (65′)