"As she knelt concernedly by the ashen-faced sailor taking his pulse, Captain Stewart noticed her hands, neat slim white fingers, almost translucent; no ring on the left hand.

"Married? he asked, as she stood up. "Widowed," she said. "In '35, a mining accident."

"Oh, sorry how stupid of me." said the Captain.

"It's alright," she said, "You were not to know."

But he did know. As head of Naval Security, Scapa Flow, he had read the briefing files on all the professional and other key personages in the Orkney Islands.

The tight security surrounding the islands was there because Orkney was of crucial strategic importance. It was the main base for the Home Fleet; from here they attacked German surface vessels and U boats moving through the Fair Isle Channel between Norway and Britain.

All mail and personnel leaving and entering the Orkney Islands was scrutinised with extreme thoroughness.

The British reckoned, that to track ship movements, German Intelligence would have at least one or two, perhaps more, agents planted in the islands. It was Captain Stewart's job to find them"