In the years leading up to the Second World War, a steady trickle of German agents make their way quietly across the English Channel where they disappear into the anonymity of the British way of life. Some feed back information to their masters in Berlin while others simply wait for the signal to act. At the outbreak of hostilities, two agents are given their assignment: An audacious theft from under the very noses of the British Secret Service who in turn are desperately trying to locate and eliminate them. But they are not alone. At the very heart of the country that they are hoping to destroy, others are quietly helping them.....