Runaway Division Two leaders Partick were brought down to earth with a 2-0 defeat by Stenhousemuir at Ochilview Park.
Thistle, 18 points clear before the match, penned the home side back for most of the first period, but the Warriors were always dangerous on the break and opened the scoring in the 30th minute.
Chris Jackson crossed into the middle and Issac English's kick beat Kenny Arthur from 12 yards for his 15th goal of the season.
Martin Hardie blazed over the home crossbar from four yards and goalkeeper Garry Gow blocked another close-range effort from the same player.
But the home side's threat was obvious when just before the break, an angled Scott Miller snap-shot hit the Thistle crossbar.
Brian Fairley's men were much more in control in the second period and when Colin McKinnon glanced a near-post header from a Nicky Henderson corner into the net after 76 minutes, there was no way back for the visitors.