Two goals from Nico Sacchetti in the third period saw the Fife Flyers come from behind to beat Belfast Giants 4-3.
The defeat is a major setback to the Giants' Elite League title hopes.
Justin Fox and Nicholas Rioux were on target for Fife in the first period, with James Desmarais finding the net for the visitors.
Colin Shields and Jonathan Boxill made it 3-2 to the Giants by the end of the second period, before Sacchetti's double ensured victory for the hosts.
Sacchetti's first goal was controversial with the Giants claiming that his shot had not crossed the line after hitting the crossbar.
The Giants were missing injured Derrick Walser, Chris Higgins and Matt Nickerson while David Rutherford was ruled out because of a one-game suspension.
Belfast play Nottingham Panthers at the SSE Arena on Sunday (17:00 GMT).