Stronghold starts with a violent casino robbery in Knokke. Criminals Jim and the badly wounded Charlie flee with the loot, but their car breaks down in the foggy Flemish countryside. They seek shelter and break into 'Wildschut', a remote, run-down farmhouse.The gangsters immediately take the resident Deleye family hostage. After Charlie dies from his injuries, the psychopathic Jim is left alone with the captives. A tense psychological mind game unfolds, filled with threat and humiliation as Jim plays the family members against each other.While a local police chief starts a clumsy search, tension builds to a boiling point. The father tries to fight back, leading to a bloody, explosive finale where the survivors must do anything to escape Jim's madness.