Steven Lawless' 95th-minute equaliser ensured Partick could celebrate their Irn-Bru Scottish First Division title in style as their entertaining encounter with Dunfermline ended 3-3.
All was going to plan for Alan Archibald's men after 27 minutes when Jordan McMillan raced onto Christopher Erskine's through ball before firing past Michal Hrivnak to put the hosts ahead.
The game was turned on its head by two goals from the Pars in the space of seven minutes, with first Ryan Wallace steering Stephen Husband's 65th-minute cross past Scott Fox.
Andrew Geggan then tapped in his third goal of the season to put Jim Jeffries' men ahead.
With 10 minutes remaining, Ryan Thomson forced home the visitors' third goal of the afternoon after the Jags had failed to clear Wallace's corner.
Thistle's promotion party looked to be ending in defeat but after Erskine had converted Steven Craig's through ball from close range four minutes later, but the Firhill crowd were treated to a late leveller thanks to Lawless' last-gasp volley.