Carried on a wave of incredible support, Argentina overcame a 10-0 deficit to eventually overwhelm Wales 29-17, as late tries by replacements Joel Sclavi and Nicolas Sanchez took them into the World Cup semifinals for the third time on Saturday.
Wales made all the early running and deservedly led after a Dan Biggar try, but the Pumas chipped back with a series of Emiliano Boffelli penalties to take the lead.
Wales was on the back foot for most of the second half, and though a Tomos Williams try briefly restored its lead, there was a sense of inevitability about Argentina's emphatic response amid a raucous sea of blue.