Fortress is a 1985 Australian thriller film directed by Arch Nicholson and written by Everett De Roche, and starring Rachel Ward, based on Gabrielle Lord's 1980 novel of the same name.

In the van, Sally and the older students overhear the men discussing holding the school for ransom, threatening to murder one child a day until their demands are met.

Pretending innocence, Sally asks the kidnappers to stop for a rest break, while secretly ordering one of the children to hide in the woods and go for help.

The kidnappers immediately realize one of their victims has gone missing and threaten to shoot one of the other children, forcing Sally to call the boy back.

Sally concocts a plan for the oldest schoolgirl, Narelle, to distract the kidnapper by flirting with him while another boy steals his shotgun.

Discovering a cave, they proceed to fortify it, using lessons they learned in class about the hunting methods of indigenous Australians to build a pit with sharpened spikes and using their school supplies to make spears.

Several months later, police investigators visit the school to speak to Sally about the condition of the body of Father Christmas.

Sally regards the preserved human heart on display among the school's science experiments, then, satisfied, dismisses the children for the day.

[6] The film was initially released directly to cable television by the HBO channel in the United States on 24 November 1985.