Blackburn were blown away by a first-half Dwight Gayle hat-trick before Peterborough withstood a second-half fightback to climb off the bottom of the npower Championship with a 3-2 win.
Darren Ferguson's men were put to the sword 4-1 at London Road in November but clinically gained revenge before a thoroughly disgruntled Ewood Park crowd.
Gayle started the match without a goal in eight appearances in 2013 but found Blackburn's defence in a thoroughly generous mood and completed his hat-trick before the 27th minute was up.
The former Dagenham forward pounced on rebounds after Rovers goalkeeper Jake Kean denied Danny Swanson and Lee Tomlin respectively, either side of a fine header following excellent work by the impressive Nathanial Mendez-Laing.
Blackburn's top scorer Jordan Rhodes netted his fourth goal against Peterborough this season but by the time on-loan Wigan midfielder David Jones - one of three half-time substitutes sent on by boss Michael Appleton - hit a deserved debut goal in stoppage time, the visitors were home and hosed.
Peterborough are now 22nd, a point behind fourth-bottom Barnsley, while a fifth league game without victory leaves Blackburn 10 points shy of the top six with their play-off hopes in tatters.
Posh should gone ahead in the third minute when Tomlin and Gayle combined to present Swanson with a glorious opportunity that he blazed over.
As usual, Rovers' main attacking threat came from Rhodes, who had a shot blocked by Gabriel Zakuani and headed over from David Bentley's measured cross before Peterborough took an 11th minute lead.
Kean produced a fine double save to thwart Swanson but Gayle was on hand to blast into the roof of the net.
Appleton's men almost found an instant response but Posh goalkeeper Robert Olejnik bravely denied DJ Campbell, and Gayle ensured he was handsomely rewarded.
Mendez-Laing comprehensively beat Rovers defender Scott Dann before his cross to the far post was misjudged by Karim Rekik, the on-loan Manchester City youngster getting underneath the ball and allowing Gayle to head home back across Kean.
A porous midfield was at the root of Blackburn's problem and Appleton brought Bentley inside into an advanced central role, deploying Campbell on the right flank. Moments after the reshuffle, however, it was 3-0.
Once again Mendez-Laing was the catalyst as he danced through a home defence offering generous helpings of time and space. He cut back for Tomlin to shoot and Kean produced another save in vain, Gayle coolly lifting the rebound over him to claim the matchball.
Rhodes uncharacteristically spurned an opportunity to hand Blackburn a lifeline, blazing from 12 yards after Olejnik kept out a Dann header, but it was almost 4-0 at the interval as Swanson drove inches wide from distance with Kean beaten.
Jones, fellow debutant Cameron Stewart and Adam Henley were introduced in place of Bentley, Bradley Orr and beleaguered captain Danny Murphy at the break, but Swanson almost compounded Blackburn's misery with a near-post effort that Kean scrambled behind.
Blackburn enjoyed longer periods of possession but clear-cut chances were not forthcoming, while Rekik produced a magnificent last-ditch tackle to deny Mendez-Laing on the counter attack.
With 17 minutes to play, Rhodes reduced the arrears in assured fashion - steeling in behind the Peterborough defence and nutmegging Michael Bostwick to earn the space for a crisp finish.
Jason Lowe had the chance to set up a grandstand finish with his first senior goal but the Rovers midfielder flashed his snapshot wide.
Jones belatedly did just that in the second minute of stoppage time, capping a fine individual display by curling beyond Olejnik from 20 yards, but too much damage had been done.