Essex 95 for 8 (Sanderson 4-24) trail Northamptonshire 390 (Procter 113, Berg 75, Young 63) by 295 runs
Ben Sanderson blasted a gaping hole in the fragile Essex batting with four quick-fire wickets to capitalise on Luke Procter's marathon century and put Northamptonshire in total command at Chelmsford.
The pace bowler took his season's tally to 15 in five LV= Insurance County Championship innings as he found the edges of a succession of bats - including the plainly out-of-form Sir Alastair Cook - that reduced Essex to 55 for 5, then 75 for 7 and finally 95 for 8 at the close in reply to Northamptonshire's 390.
Essex had no bowlers of similar ilk as Northamptonshire were able to eke out a further 157 runs to their overnight score in 45 overs, courtesy of a tortoise-and-hare ninth-wicket partnership of 105 between Procter and Gareth Berg.
Procter took exactly six hours to carefully compile his 113, only the fifth century of his 12-year first-class career. In contrast, Berg included three sixes in a swashbuckling 75 that lasted just 132 balls.
Northamptonshire now stand on the threshold of instant revenge after their humiliating innings defeat inside four sessions on the same ground only seven months ago.
The rot set in for the home side as early as the fifth over of their response when Nick Browne went cheaply, nicking Sanderson to second slip. Tom Westley followed on the stroke of tea when playing down the wrong line to hand Will Young a second catch, this time off Tom Taylor's bowling.
At least Westley's 25 came from 50 balls. Cook, by contrast, looked completely out of nick as he scrabbled around for an hour and a half for six before falling caught behind to the 48th ball he faced.
Young completed a hat-trick of catches, swooping after Emilio Gay at third slip had parried Matt Critchley's edge in his direction. And Gay picked up a catch of his own to send back Paul Walter for 2 that had taken 39 balls and given Sanderson wicket No. 4.
Adam Wheater adopted a brief aggressive cameo with three fours in an over from Matt Kelly. But the Australian seamer made amends, knocking back middle-stump when Wheater ushered the ball through having erroneously decided not to play a shot.
Simon Harmer caught the bug and also shouldered arms to Kelly and was lbw for nought. Feroze Khushi took 36 balls to score his first run and had reached 9 16 balls later when he was caught behind to make Procter's day complete.
On a bitterly cold and overcast day, the green wicket continued to play slow and low - at least until the point where Essex went in to bat when it revealed hitherto unheralded terrors.
The early dismissal of Kelly did not preface the swift end to the Northamptonshire innings for which Essex had budgeted. Rather it teamed Berg with Procter.
Kelly had tried to inject some aggression into his innings, but only succeeded in pulling to short midwicket to give Shane Snater a third wicket in eventual figures of 3 for 56.
Berg refused to be tied down and clobbered Critchley over midwicket for six that ran counter to Northamptonshire's otherwise softly-softly approach. He later twice threatened the scorers' box when lofting the same bowler straight for further maximums.
Procter, who lunched on 99 after adding just 39 to his total in the morning session, duly passed three-figures post-break when he turned Mark Steketee backward of square for two. He had faced 256 balls to that point.
However, in an uncharacteristic moment of madness, the left-hander attempted to hit Critchley out of the park for what would have been just the 11th boundary of his innings, only to pick out the imposing presence of Paul Walter at short midwicket.
Berg finally went after a mini-flurry of hitting when he found Westley on the long-on boundary to give Critchley figures of 3 for 81.
