1649. Oliver Cromwell and his New Model Army have arrived in Ireland and are laying siege to the town of Drogheda. 10-year-old twin brother and sister, Liam and Aoife O'Keeffe, are trapped inside. When the soldiers manage to break through the walls protecting the town, they start killing the men, women and children. Liam and Aoife manage to escape and decide to try to warn other Irish towns of the dangers of Cromwell and his ruthless army. Can they reach the towns in time, and can anyone stop the relentless march of 'the most hated man in Irish history?'