Ton had started the game in whirlwind fashion; Myles Hogarth in the Albion goal stopped a Jim McAlister drive with his foot and then palmed away a Derek Lilley effort which fell to Paul McGowan whose low shot was deflected past by the busy keeper.
Peter Weatherson had a firm drive saved by Hogarth but then Albion forged their way into the game, Weatherson managing to head a John Fraser shot away for a corner when it was destined for the top corner of the net.
Nathan Taggart's speed and skill sorely tested Weatherson and one of his crosses was volleyed over by Colin Cramb.
Douglas Wilson threaded a superb ball through for Cramb but, having placed the ball beyond Stefan Gonet, the striker watched in mortification as the ball hit a post, rolled along the line and was cleared.
Ton attempted to regain the initiative after the break but Lilley's cross, after he had beaten Hogarth to the ball, was headed weakly wide by Chris Millar.
Hogarth denied McAlister and the game seemed destined for a goalless stalemate when Muir decided that Marek Tomana had impeded Millar, a decision which infuriated Albion. Lilley headed in Jamie Stevenson's free-kick from six yards.
In stoppage time, Muir penalised Stewart Greacen when the ball struck his hand after he had made a headed clearance. Chris Aitken beat Gonet from the spot with ease, leaving the home support none too pleased.