A major theme is Marks's inability to convince his superiors in the Special Operations Executive (SOE) that apparent mistakes made in radio transmissions from agents working with or in an alike role as the Dutch resistance were their prearranged duress codes, which it transpired they were as he alleged, and which fact haunted him.
Marks's persistent efforts to convince his superiors at the SOE about the supposed mistakes in radio communications from agents working alongside or in a comparable role to the Dutch resistance ultimately proved unsuccessful. It was later revealed that these "mistakes" were actually prearranged distress signals, which continued to weigh on Marks.