Ollie Watkins broke Pompey’s hearts with a 90th-minute leveller at Exeter City.
Watkins struck late on to deny Paul Cook’s side a much-needed victory in the League Two encounter.
Conor Chaplin produced a moment of quality to drive his side in front after 31 minutes.
Chaplin had other first-half chances – as did Pompey old boy Jayden Stockley.
It was another dogged performance full of perspiration rather than inspiration for Pompey.
And it looked like a win would see them close in on some promotion rivals – until the late Watkins intervention.
Pompey had a great chance to break the deadlock after just 22 seconds but Chaplin’s control let him down when well placed from Kal Naismith’s cross.
Both David Wheeler and Christian Burgess then headed chances over as the play switched from end to end.
Michael Doyle had a 25-yarder well saved by Bobby Olejnik after 25 minutes.
That miss didn’t matter five minutes later, as Chaplin broke the deadlock out of the blue with a driven finish from the edge of the box.
Chaplin could have doubled the advantage after 33 minutes but scuffed his shot wide from 10 yards from Marc McNulty’s cross.
Pompey were looking comfortable but Exeter finished the half strongly as Ryan Fulton dived full length to keep out Watkins’ drive.
Stockley, who had earlier missed a decent chance with his head, then put another header wide moments before the break.
Kyle Bennett dragged a shot well wide after a promising run moments after the restart.
Naismith then wasn’t far away as he tried his luck from 35 yards after 59 minutes.
A never-say-die attitude nearly produced a second for Pompey, as Chaplin chased down Olejnik and managed to hook a shot at goal as he was floored. The ball tricked inches wide.
Stockley missed another chance against his old side after 63 minutes, when he outmuscled Webster and poked a shot wide from a corner.
Naismith then won a free-kick on the edge of the box as Pompey threatened on the break. Chaplin fired inches over the top from 20 yards.
Alex Nicholls blazed over as the home side pushed forward with time ticking down in the rain in Devon.
But then came Watkins’ leveller with seconds left of normal time, as he wriggled through on the byline and poked agonisingly past Fulton.