Steve Magoffin broke the back of the Durham innings to give Sussex the chance of claiming an important LV= Championship Division One victory at Arundel.
The Queenslander took four for 14 in an outstanding 10-over spell with the new ball before rain curtailed Durham's second innings on 80 for seven with an hour remaining on the third day.
It means they lead by 80 after Sussex were dismissed for 231, to leave the scores level after the first innings, and their hopes largely depend on skipper Paul Collingwood, who is 29 not out.
Magoffin took his wicket tally for the season to 32, striking first when Mark Stoneman was leg before in the fourth over offering no shot.
In his next over Magoffin profited from the erratic bounce at one end to pin Gordon Muchall for a duck with a ball which kept low.
While Muchall could consider himself unfortunate, Ben Stokes was dismissed in soft fashion, caught at mid-wicket looking to work Magoffin through the leg side in his fifth over.
Will Smith and Dale Benkenstein staged a recovery of sorts to take the score to 29 before they fell in successive balls after tea.
James Anyon, having been struck for four boundaries earlier in the over, hit back to have Smith caught behind as he pushed forward and Magoffin claimed his fourth victim with the next delivery when Benkenstein fell in identical fashion.
Anyon gave way to Kirk Wernars who struck with his first ball as Phil Mustard mis-timed a pull to mid-wicket and the seventh wicket fell in the 22nd over when Scott Borthwick was caught behind off Luke Wright playing defensively.
Collingwood and Calum Thorp added 18 more runs before the heavens opened.
It was certainly a day for the bowlers with 15 wickets falling, seven of them lbw. There was seam movement throughout and as a soft pitch dried out so the bounce became more unpredictable.
Sussex had been indebted to skipper Mike Yardy and Ben Brown who both made half-centuries before their last four wickets fell in 21 balls for the addition of ten runs.
Yardy relished the often attritional battle but still hit seven fours in his 66, made off 170 balls.
Dropped on 55, he was eventually lbw to Collingwood having added 66 in 23 overs with Brown.
Sussex were eyeing a sizeable first-innings lead on 221 for 6 but they collapsed horribly to the second new ball. Calum Thorp picked up Wernars and Magoffin with successive deliveries while Brown was defeated by a shooter from Steve Rushworth after hitting seven fours in his 51.
Sussex were still ten behind having lost three wickets in eight balls but Monty Panesar struck a couple of boundaries to level the scores before Rushworth had him caught at mid on to end the innings.