Owls youngster Tommy Spurr struck with a late leveller to wipe the smile of the face of former Owls boss Paul Sturrock.
Wednesday were heading for defeat and Sturrock looked set to put one over on his old club as Plymouth Argyle tried to keep their flickering play-off hopes alive.
Hungary international Peter Halmosi gave his side the lead when he struck with a second minute goal, but Wednesday, staring relegation full in the face, hit back as Spurr smashed in a 20-yard volley.
The Pilgrims had the perfect start when they went in front after less than two minutes in front of Wednesday's stunned Kop.
Adam Bolder, two-goal hero of last week's 2-2 draw with Sheffield United, gave away the game's first foul when he clattered Nadjim Adbou.
Halmosi, back in the Plymouth side after a two-match injury absence, took his time to size up the chance before crashing in a left-foot shot.
The well-struck effort flicked off Deon Burton on the end of the Wednesday wall and looped past keeper Lee Grant.
Wednesday recovered from the shock setback, but Franck Songo'o wasted a free-kick as he took it quickly and hit it straight at Luke McCormick.
Twice Jermaine Johnson found space wide on the right but a dangerous low cross was turned wide from six yards by Burton and then Johnson's angled shot went wide.
And in the dying seconds of the first half Johnson volleyed over and Bolder blew a golden opportunity, firing wide after Ben Sahar slipped a neat ball through.
Wednesday won a free-kick 20 yards out after 73 minutes, just as the Yorkshire side began to run out of ideas.
Songo'o and Wade Small stood over it and it was the former who struck a sweet shot that cleared the wall and swung goalwards, but McCormick dived to his right and turned it away.
Another dangerous ball from Songo'o, a cross from the right, was aimed for Bartosz Slusarski at the far post but McCormick claimed it comfortably.
Another later save from McCormick preserved the lead, as he got down smartly to his right to deny Burton following Spurr's throw-in.
But nine minutes from the end Spurr struck the sweet leveller and his effort was enough to drag Wednesday out of the relegation zone at the expense of Leicester City.