Steve Evans' non-league Crawley won through to the FA Cup fifth round for the first time thanks to a 39th-minute winner from top scorer Matt Tubbs that earned them a 1-0 win over Torquay.
Tubbs took his season's tally to 25 goals to put the Blue Square Bet Premier side ahead, and the win could have been even more comfortable for the side from West Sussex if either Tubbs or Craig McAllister had converted second-half penalties.
Both sides finished with 10 men, as Chris Zebroski was sent off for the hosts after an hour and Dean Howell followed seven minutes from time for Crawley, who now go on to the last 16.
Tubbs' decisive goal came when he beat the offside trap to latch on to a ball over the top from Dannie Bulman before slotting home past United goalkeeper Scott Bevan.
The Gulls number one kept his team in the tie with two spot-kick saves in the space of six minutes.
Zebroski was red-carded after receiving his second caution in a minute for handball in the area, and Tubbs sent his penalty to Bevan's left but the goalkeeper used all of his 6ft 5in frame to push the ball around his post in spectacular fashion.
A few minutes later, Bevan produced a second penalty save, this time denying McAllister to his right after United skipper Lee Mansell was adjudged to have fouled Crawley's Jamie Cook.
Left-back Kevin Nicholson looked to have levelled with an audacious 87th-minute volley from the left wing that swerved over Crawley goalkeeper Michel Kuipers but bounced off the top of the crossbar.
Crawley were reduced to 10 men in the late stages when defender Howell received a second yellow card, but they held on.