Basement side Torquay upset third-placed Southend 1-0 at Plainmoor, ending the Shrimpers' seven-match unbeaten run in all competitions.
On-loan Millwall striker John Marquis, 21, fired the Gulls ahead with a superb angled strike from the left on 50 minutes, following a defence-splitting lob from recalled winger Billy Bodin.
Torquay may well have gone two in front within a minute as Southend cleared the ball off the line in a goalmouth scramble and from the corner on-loan Leicester playmaker Jak McCourt bounced his pacy inswinging cross off the bar.
Gulls midfielder Damien Mozika came closest to breaking the first-half deadlock, heading inches wide from Jordan Chapell's cross from the left in the 31st minute.
Earlier, home skipper Lee Mansell's 18-yard shot was deflected over the bar by defending Southend striker Barry Corr, who got his head to the goal-bound strike.
Corr was also in the thick of action when he was injured helping Southend keeper Daniel Bentley clear a 43rd-minute corner from Aaron Downes' head.
Torquay boss Alan Knill handed a first start of the season to fit-again keeper Michael Poke.