With Rod away on urgent Mines Department business, leaving Les in charge, Sam and Ben battle a dangerously steep ramp underground. After sinking a new shaft to save their backs, the Bushmen are stonewalled by impenetrable rock. It's the last dig of the season, and Dan and Renee are fighting ultrahard rock. It's a Hail Mary search for opal at Benito's until dusty gusts force the pair to return at night when they encounter thieving 'night-shifters.' After a season-long battle against an unyielding rock cap, the Mooka Boys are finally ready to tunnel toward black opal glory until their last working machine suffers a catastrophic breakdown.