A probation officer, Cathy Madden, is tasked with rehabilitating a notorious killer named 'Bloody' Mary Laidlaw back into society following a two-decade sentence.

With nowhere else to hide, a group of mercenaries and their two prisoners take cover inside a long abandoned Bulldog tank. But, while they try to keep the forces outside at bay, the real enemy is already among them, locked inside the 'Belly of the Bulldog'.