January 1942. Two security officers visit Edwin to gain information about John Porter. Some weeks ago they traced a transmitter in Belgium. When asking for name, rank and number of the person calling, the answer was John Porter followed by some personal details. It could be a trick by the Germans, but it could also be John, locked up by a resistant group, who uses his technical skills for their own purpose. At the same time Robert is crossing the Atlantic Ocean with his ship, who is escorting a tanker with aviation fuel from New York to England. German submarines ...