Sussex star Luke Wright made his second hundred of the season against Middlesex to keep the Division One leaders in with a chance of avoiding their first four-day defeat of the season.
The England T20 all-rounder was unbeaten on 151 at stumps on day three with Sussex 288-6, a lead of 21.
It was an unlikely scenario after Steven Finn, dropped by the England team, took two wickets in his first seven deliveries in front of selector Ashley Giles.
Finn did not come on to bowl until the 17th over but with his fourth ball he had Luke Wells caught at second slip.
Then, with the first ball of his next over, he had Rory Hamilton-Brown held at first slip and he went on to bowl a ten-over spell in high temperatures and sometimes at express speed.
As well as Finn and Wright's impressive performances, Monty Panesar completed a five-wicket haul in the morning.
Middlesex resumed on 445-5, a lead of 216, with John Simpson (39) and Gareth Berg (26) the unbeaten batsmen.
Berg had added 13 when he was caught at long-off by Steve Magoffin off Panesar. Chris Jordan then had Simpson caught behind before Panesar claimed the last three wickets.
Ollie Rayner, the former Sussex player, was lbw, Tim Murtagh stumped and Corey Collymore was last out, caught behind.
That gave Panesar, who had often bowled indifferently this season, figures of 5-95 but Middlesex still had a lead of 267 after being dismissed for 496 and when Sussex subsided to 45-4 a three-day finish looked likely.
Chris Nash was out without scoring when he appeared to glove Murtagh to slip, though the batsman didn't look happy with the decision.
Sussex then lost three wickets for three runs in the space of ten balls. Between the double strike by Finn, Collymore had Mike Yardy caught behind for 18.
Skipper Ed Joyce and Wright counter-attacked, adding 110 in 25 overs, the first stroke-making and the other hitting violently.
Joyce had hit six fours in his 84-ball 47 when he was caught behind off Neil Dexter but then Ben Brown (38) came in to support Wright in another century partnership, this time worth 107.
Brown fell just before the close but Wright was still there, having faced 170 deliveries and hit 24 fours and a six.