Sussex's left-arm spinner Ashar Zaidi took four wickets to check title-chasing Yorkshire's progress on a rain-affected third day of the LV= County Championship match at Hove.
Rain and bad light restricted the day's allocation to 42 overs and Yorkshire's hopes of making further inroads into leaders Durham's advantage at the top of Division One suffered after a batting collapse saw them bowled out for 326.
Ryan Sidebottom then bowled Luke Wells with the third ball of Sussex's second innings and when bad light ended play Sussex had reached 48-2, a lead of 14.
It was an excellent day for Zaidi, who is playing his first first-class game for nearly four years.
Born in Pakistan, but now English qualified, Zaidi has been playing Lancashire League cricket for Accrington this season and the 32-year-old got his opportunity after a successful trial in Sussex's second XI last week, when he scored 192 and took six wickets.
He struck with his fourth ball on Friday when Gary Ballance's attempted sweep ballooned up off his glove and Matt Prior came across from slip to take the catch.
Zaidi then had Adil Rashid taken at mid-on off a mis-timed drive and ended the innings when he deliberately bowled well outside off stump as Liam Plunkett came down the pitch and was easily stumped.
Zaidi finished with 4-57 while Steve Magoffin again bowled superbly after play re-started at 2.10pm. The Queenslander reeled off 12 overs at a cost of 30 runs while picking up the wicket of nightwatchman Steve Patterson, who was caught behind when Magoffin managed to extract some extra bounce.
Kane Williamson had earlier been leg before to James Anyon without adding to his overnight 80, while Lewis Hatchett removed Sidebottom's middle stump as he made room to play through the off-side.
Yorkshire did secure a third batting bonus point and while their lead was a modest 34, they did not take long to make inroads when Sussex went in again.
Sidebottom bowled Wells with a superb in-swinger and Sussex lost their second wicket on 33 when Yardy drove Plunkett's fourth ball to cover where Phil Jacques took an excellent low catch.
As the light deteriorated, Yorkshire skipper Andrew Gale was forced to bowl spin at both ends but umpires Mark Benson and Steve O'Shaughnessy still considered it too dark and took the players off 45 minutes before the scheduled close.