Autumn 1940. German forces are massed along the French coast, poised to invade mainland Britain.
When they do, it is swift and brutal. Newport is blitzed. Irishman Danny O’Shea’s house is bombed and his wife is killed. Horrified by what he witnesses, O'Shea decides to take his young son Adam to the safety of neutral Ireland.
Penniless and desperate, they head for Fishguard. But on an isolated Welsh road, they witness an attack on a German convoy by Welsh insurgents. The convoy is carrying mysterious boxes discovered by the Germans in a secret laboratory near Brecon. O’Shea and Adam are detained by the insurgents on a remote farm.
Meanwhile, German Captain Eric Weiss, responsible for the boxes' safe transfer to Berlin, knows that his job - even his life - depends on him getting them back.
But the insurgents fall out and the boxes disappear. Then O’Shea goes to the aid of a dying woman - and both the Germans and the insurgents believe she’s told him where the boxes are hidden.
Suddenly, O’Shea is separated from his son and catapulted into a world of betrayal and brutal double-cross. Pursued by both the Germans and the insurgents, his only concern is to find Adam and get him to safety.