Jack Shantry-inspired Worcestershire enjoyed the better of day three in their rain-ruined LV= County Championship Division Two promotion clash with Essex at New Road.
Shantry produced a brilliant championship-best return of 7-69 and Essex were indebted to in-form Tom Westley's battling 90 as they eventually posted 215.
The seventh wicket went down with only 115 on the board but Sajid Mahmood, making only his second appearance since moving from Lancashire, joined the impressive Westley in a rescue partnership of 91.
When Shantry was cutting through the middle order, capturing 4-10 in 26 balls, Westley was in danger of being left in isolation, but the arrival of Mahmood forced Worcestershire on to the back foot.
The former England fast bowler bombarded an all-seam attack with 11 fours and it was a surprise when he was bowled behind his legs to give Shantry the fourth five-wicket haul of his career.
Mahmood was close to a run-a-ball in making 54 - a 10th first-class half-century - but his departure sparked another damaging spell, in which Shantry claimed the last three wickets for four runs in 10 deliveries.
Westley, having batted with such control until the 62nd over, allowed his judgment to lapse. Needlessly taking on Shantry, he was caught at long-on and missed an opportunity to join a list of 10 players who have carried their bat for Essex.
With only 6.5 overs bowled on the first two days, a badly curtailed match has come down to a battle for bonus points.
Worcestershire will start the final day with a clean slate after rain at 5.30pm halted their reply on nought for nought in two balls from David Masters.
At least there was good progress when Essex resumed their first innings at nine for one. Debutant Nick Browne, offering no shot, and Mark Pettini, propping half-forward, fell to Alan Richardson, the leading wicket-taker in Division Two.
Ryan ten Doeschate, in his second match since returning from IPL duty with the Kolkata Knight Riders, struck three fours in nine balls but a collapse set in when he edged Shantry to second slip.
Bowling from round the wicket, Shantry suddenly hit a hot streak. Ben Foakes, leg-before, and James Foster, nicking to first slip, went in successive balls and Graham Napier, having hit a couple of fours, flashed a fierce head-high catch to Gareth Andrew in the gully.