Steven Craig's second-half strike was enough to send Partick through to the Ramsdens Cup final with a 1-0 win over Cowdenbeath.
Craig pounced with 16 minutes remaining, tucking the ball away after he was played in by Steven Lawless.
Partick should have gone ahead after quarter of an hour but Thomas Flynn made a double save to deny Chris Erskine and Paul Paton before Lawless headed wide.
The busy Flynn then tipped a shot from Stephen O'Donnell round the post and from the corner, Aaron Muirhead nodded over.
For Cowdenbeath, Kenneth Adamson headed over and Thistle keeper Scott Fox kept out a fierce drive from Marc McKenzie.
And at the death Flynn came up for a corner but could only plant his header wide.