Jayden Stockley scored deep into stoppage-time to complete a remarkable comeback and secure a point for Pompey against Morecambe.
The visitors rocked their hosts with first half goals from Tom Barkhuizen, Alan Goodall and Andy Fleming.
But a couple of fine Gary Roberts strikes either side of the interval brought the Blues right back into the game.
Enda Stevens’ dismissal for two bookable offences failed to halt their attacking intent as Pompey poured forward at every opportunity.
And their perseverance was rewarded in the fifth minute of stoppage-time when Stockley dived to head home the equaliser.
Paul Cook named an unchanged side, as he elected to use the same starting 11 for a fourth successive league match.
That meant Ben Davies – who went off at Crawley during the week – had sufficiently recovered from a hamstring injury to take his place at right-back.
Pompey looked to attack straight from kick-off and a neat move ended with Nigel Atangana firing over in the opening seconds.
Stevens then skipped into the box before Adam Dugdale came across to thwart him, before Matt Tubbs could not quite guide a corner on target.
The hosts were dominating possession yet again, but were caught with a counter-attacking sucker punch on 11 minutes.
Michael Doyle slipped and Davies’ clearance ricocheted into Barkhuizen’s path, with the wide-man smashing a shot past the helpless Brian Murphy.
The goal seemed to rock the Blues and a period of sluggish play ensued, with Cook’s men guilty of far too many misplaced passes.
However, Pompey started to move through the gears again and Roberts guided Stevens’ pass narrowly past the post.
But the Shrimps soon doubled their advantage after Christian Burgess had been booked for a foul on Aaron Wildig.
A diving Murphy was able to palm Jamie Devitt’s free-kick behind, but the Morecambe midfielder’s resulting corner was headed home by Goodall.
Wildig then tried to catch Murphy out with a neat chip that dipped onto the crossbar before the same played dragged a shot wide.
Shrimps keeper Barry Roche was booked for taking too long over a goal-kick on 36 minutes, although the visitors arguably did not need to waste time as they continued to open the Blues up on the break.
And they soon went three goals ahead when Fleming arrived at the far post to steer home Devitt’s cross.
Pompey looked all at sea, but there was a glimmer of hope late in the half when ROBERTS was brought down on the edge of the box and picked himself up to curl home an impressive free-kick.
Davies had a chance for the Blues soon after the restart, with a close-range volley that hit Dugdale in the face and flew safe.
There was then danger at the other end when Matt Clarke under-hit a pass, but the teenage centre-back recovered well to win the ball back.
And Pompey were soon back on the attack and Tubbs rose to glance Kyle Bennett’s cross inches wide, although it would not have counted as the linesman’s flag was raised.
The hosts were not having any trouble getting hold of the ball, but Roche was not being overly tested between the sticks.
They did reduce the deficit further thanks to another moments of magic from ROBERTS on 65 minutes, however.
The midfielder picked the ball up and deceived a couple of defenders with his footwork before curling a shot into the bottom corner.
Cook freshened up his front line with a substitution on 70 minutes, as Tubbs made way for aStockley.
But the Blues were soon reduced to 10 men when Stevens caught Aaron McGowan and was shown his second yellow card – and a subsequent red – by referee Roger East.
Adam Webster was brought on for Davies as Pompey switched to playing with three central defenders.
They were leaving plenty of men forward, safe in the knowledge that Morecambe were happy to sit back and soak up pressure.
Cook made his final change on 80 minutes as Adam McGurk replaced Gareth Evans and immediately received a chance to level when he rose to head Bennett’s cross narrowly wide.
Bennet then had an opportunity of his own, cutting inside and drilling in a shot that Roche did well to punch clear.
Morecambe were hanging on and Roche pushed Clarke’s header over before keeping out a Stockley drive.
And Webster missed a great opportunity after being left unchallenged in the box, only to head over.
The defender then saw his penalty claims for a handball waved away as Pompey continued to pour forward.
And just when it looked like time would run out on them, Webster delivered a perfect cross for STOCKLEY to convert with a diving header.
Pompey (4-2-3-1): Murphy; Davies (Webster 74), Burgess, Clarke, Stevens; Atangana, Doyle (c); Evans (McGurk 79), Roberts, Bennett; Tubbs (Stockley 70)
Goals: Roberts 42, 65, Stockley 90+5
Sent off: Stevens (two yellow cards)
Subs not used: Jones, Haunstrup, Hollands, Chaplin
Morecambe (4-2-3-1): Roche; Beeley (c), Dugdale, Parrish, Wilson; Fleming, Goodall (Kenyon 47); Devitt, Wildig, Barkhuizen (Molyneux 56); Miller (McGowan 68)
Goals: Barkhuizen 11, Goodall 25, Fleming 38
Booked: Fleming, Roche, Beeley, Wildig
Subs not used: Thompson, Bailey, Ryan, Mullin
Referee: Roger East