It was the moment that turned the Six Nations Test match in favour of Scotland as the visitors quick thinking ruthlessly exposed Wales as they switched off in defence.
It allowed Scotland replacement wing Darcy Graham to score the try that changed the game.
Wales were leading 23-12 in the 58th minute after replacement fly-half Jarrod Evans had just slotted over a penalty.
An efficient home ball boy quickly presented the ball on the halfway line for Scotland to take a quick restart and Finn Russell and Graham did the rest.
Russell took a quick drop out towards the vacant Welsh right hand side which caught the home defence napping.
Wales replacement flanker James Botham, who had an outstanding match, watched the ball drop over his shoulder with Graham, who had just come on the field, reacting the quickest.
Graham outsprinted Wales wing Gabriel Hamer-Webb - who was running back after following up Evans' penalty kick - to stun the hosts with Russell's conversion reducing the deficit to four points.
The momentum switched with Scotland going on to win the game and break Welsh hearts.
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'Another harsh lesson for Wales' - Tandy
"It was huge in the game," said Wales head coach Steve Tandy.
"Test match rugby, you need to make people work for their opportunities and we feel we didn't do that in that moment.
"We were looking to extend the lead. It gave Scotland energy, where if we take the kick-off and get it off the field, that's seconds off the clock.
"It's another harsh lesson in some of the games. In high-class games, you can't knock off.
"We backed up moments in the game and handled our yellow card pretty well.
"There was some great stuff, the intent and physicality from the group was there, but that moment cost us."
What the pundits say
Former England World Cup winning-captain Martin Johnson on BBC One: "Wales will wake up tomorrow and they'll think the try straight off the kick-off has cost them the game. Not looking at the ball after a kick-off has cost them.
"It all comes down to fundamentals. That was such a huge moment, it changed the game completely."
Former Wales fly-half Jonathan Davies on BBC One: "The turning point was that Darcy Graham try.
"At international level you cannot allow opposition to score a try straight from the restart when you've got 15 players in your own half."
Former Wales wing Alex Cuthbert on BBC Radio Wales: "If you gave me this result before the game I would've taken it, but I think how it was just one moment [Darcy Graham's try] that got Scotland back into the game makes it so much harder to take.
Former Scotland flanker John Barclay on BBC One: "Credit to Scotland for being brave.
"The game swung on the Darcy Graham try. Wales were brilliant, Scotland got away with that."