There was no last-day great escape from Dumbarton as, for the second time this season, they blew a two-goal lead against the Jags - although Alloa's win at Kirkaldy made this result academic and the Sons will be playing Third Division football next term.
Partick's place in the promotion play-offs was secure and they seemed content to simply play out this fixture. However, they received a real jolt as Andy Rodgers netted twice for the home side just before the break, the first a scorching shot from the edge of the box high to Kenny Arthur's left, the second an easier affair after Chris Boyle's long ball had sent him clear on goal.
Thistle moved up a gear after the interval, at it was no surprise when Stephen McConalogue latched on to Billy Gibson's neat defence-splitting pass to slip the ball under the advancing Stephen Grindlay.
Rodgers drove an effort against the outside of a post from a tight angle, but the Jags deservedly drew level when Billy Gibson's low ball across the face of goal provided an easy tap-in for Mark Roberts.
The winner came three minutes from time and summed up the Sons' season: Grindlay raced from his goal to prevent a corner but only succeeded into pushing the ball to the feet of McConalogue, who duly rolled it into the empty net.