Andre Green was the late, late hero as Pompey took the scalp of Championship high-fliers Norwich.
Sub Green struck with virtually the last kick of the game to send Kenny Jackett's men into the fourth round against the 10-men Canaries with a 1-0 success.
The late drama sent the delirious 2,493 travelling fans wild as the Blues moved into the fourth round for the first time in three years.
That was after the home side played for 75 minutes with 10 men following skipper Grant Hanley’s dismissal.
A first-half miss from skipper Brett Pitman looked likely to be costly against Daniel Farke’s Premier League chasers in an entertaining affair.
The ability of the Canaries was evident even a man light, but Jackett learnt much about their side’s ability to punch their weight with a quality second-tier outfit.
Pompey were forced on the back foot through the game’s opening as the home side dominated possession and moved the ball around fluently.
Their fluid approach wasn’t pulling the visitors out of shape, however, although Kenny McLean fired over from 25 yards after 11 minutes.
There was a big moment four minutes later as the home side were reduced to 10 men as Hanley was given his marching orders.
Ronan Curtis was bursting through on goal and was hauled down 30 yards out, and referee Darren Bond decided it was a clear goalscoring opportunity leading to the Canaries skipper being given his marching orders.
There was a gilt-edged chance for the visitors two minutes later as Lowe delivered a perfect cross for Brett Pitman, but he wastefully headed over from a few yards out.
The home side were still a threat despite being a man light with defender Christoph Zimmermann smashing a 30 yarder not too far past the upright and Ben Marshall having a 27th-minute free-kick comfortably saved by Craig MacGillivray.
A Norwich free-kick saw shots from Jordan Rhodes and Ben Godfrey blocked in the 35th minute.
Matt Clarke then saw his cross blocked after a trademark marauding run down the left.
A thumping effort from Gareth Evans was blocked by Godfrey in the 39th minute as the game swung from end to end.
There were no goals as the sides went in at the break, however.
Tom Naylor fired the first chance of the second half at Michael McGovern from 20 yards, two minutes after the restart.
Then Pitman blasted another chance not too far over the two with a dipping 20 yarder two minutes later.
Curtis glanced a header past the post in the 51st minute from a decent Dion Donohue cross.
Despite being a man light it was the home side having the better of possession with their second-tier quality obvious.
Todd Cantwell flashed a shot wide in the 58th minute and then Anton Walkes produced an excellent last-ditch tackle to deny Dennis Srbeny in the box.
Andre Green was introduced in place of Evans in the 67th minute.
The game was still bouncing from end to end as being played at a pace, despite no goals.
Donohue then saw his 25 yarder spilled by McGovern in 77th minute with Pitman unable to force the loose ball.
Two minutes later it was Lowe who forced McGovern into a sprawling save with a 25-yard effort.
Lowe’s cross then was cleared by Zimmermann with Pitman waiting for the tap-in before Thompson’s 25 yarder dipped narrowly over via a deflection.
There were three minutes of stoppage time indicated at the end of the game.
And that allowed the time for Green to make the difference as he fired home at the second attempt after good work from Donohue.
There were chants of Que Sera Sera from the travelling faithful on the final whistle as another high was hit in what is developing into a season to remember.