Halla is a middle-aged independent woman. But behind the scenes of a quiet routine, she leads a double life as a passionate environmental activist. Known to others only by her alias “The Woman of the Mountain,” Halla secretly wages a one-woman-war on the local aluminium industry. As Halla's actions grow bolder, from petty vandalism to outright industrial sabotage, she succeeds in pausing the negotiations between the Icelandic government and the corporation building a new aluminium smelter in the mountains. But right as she begins planning her biggest and boldest operation yet, she receives an unexpected letter that changes everything. Her application to adopt a child has finally been accepted and there is a little girl waiting for her in Ukraine. As Halla prepares to abandon her role as saboteur and saviour of the Highlands to fulfil her dream of becoming a mother, she decides to plot one final attack to deal the aluminium industry a crippling blow.