Chapter 26 The Unfamiliar Hand

The morning after the hangar was grey and quiet, as if the night had used up all the weather and left nothing behind but a low, patient sky. Margaret Chase came into the office at half past eight, hung her coat on the same hook, and found the courier pouch already waiting on her desk, because that was what the war had made of her and what the peace had left her to be: a woman who arrived on time and opened the mail that other people were afraid to touch. She worked through the pouch methodically, setting the routine traffic aside in neat stacks, and when she came to the message she had decoded the night before, she did not set it aside. She smoothed the paper flat on the desk and looked at it the way a gardener looks at a weed that keeps coming back in the same corner of the bed, however often it is pulled. Margaret Chase. We know the woman who kept the keys. We know the name of the man who taught her. The long night is over. The new one is beginning. The woman who kept the keys was in a cell at Scotland Yard. The man who taught her was a name Margaret did not yet have. And the cipher it was written in was the thing that troubled her most of all, because she had never seen anything quite like it. It was not Enigma. It was not Hayes's private code. It was not the ghost-key traffic that Edith Crane had fed to Germany for four years. It had the look of a one-time pad, the infinite key that cannot be broken, except that nothing is infinite, and pads are made of paper, and paper gets used twice. She had found it by accident at half past three in the morning, when her eyes were going grey and she was ready to set the thing aside as unbreakable. The message was short, barely three lines of ciphertext, and she had been idly running the tail of it against a stack of old intercepts when the rhythm had suddenly, sickeningly, matched. A fragment of key that had been used in a German naval intercept logged in September 1942. Four years and six months earlier. Whoever had written this message had built it on the bones of an old key, the way a man builds a wall with bricks from a house that has burned down. You cannot use a key twice, Peggy Winslow said when Margaret showed her the match. She was sitting on the corner of the desk with her ink-stained fingers wrapped around a cup of tea, and her face wore the particular expression it took on when something was wrong in a way that interested her. The whole point of a pad is that each sheet is used once. If they reused a fragment, they either did not know what they were doing, or they wanted it read. Or they wanted it read, Margaret said. They spent the morning doing what the sender had intended them to do. The reused fragment gave them the shape of the key stream, and the shape of the key stream gave them the frame of the message, and by noon Margaret had the plaintext in front of her, word for word, exactly as she had read it the night before, because the sender had never meant for it to stay secret. The message had been sent to be decoded. It had been sent to be read by her, and by her alone, and it had been sent to tell her one thing. The man who taught her. Edith Crane had been taught. Margaret sat with that thought for a long time. Edith Crane had been a girl from a fishing village on the coast of Norfolk, nineteen years old when the war came for her, quiet and efficient and utterly reliable, and somewhere in that girl's past there was a teacher. A man who had taught her to set keys and to read traffic and to build a network inside a building full of the cleverest people in England without any of them ever seeing her. That kind of teaching left marks. It left habits. It left a shape in a woman's work that a woman who had spent her life reading shapes could learn to recognize. She took the message to Brennan in the afternoon, and she watched him read it in the small crowded room with the filing cabinets and the single window. He read it once, and then again, and when he set it down his face had the careful blankness she remembered from the winter of 1943. The Fisherman, he said. Margaret waited. We have a file on him, Brennan said. It is thin, and it is mostly guesswork, and it has been open since 1946. A German signals instructor named Helmut Voss, Abwehr, stationed on the coast near the Dutch border during the war. He disappeared in the spring of 1945, and our people in Berlin are fairly certain he did not die. They believe he was picked up by the Russians in the summer of 1946 and that he is still working for them now. The hand that wrote the keys for Germany is writing keys for a different reader. That is what Edith Crane said to you in the hangar. I think she was telling you about her teacher. Voss, Margaret said. The name meant nothing to her. But the shape of it, the shape of a man who taught a girl in a fishing village to build a network and then walked away and let her fall, felt suddenly familiar, the way a chord sounds familiar even when you cannot name the song. He taught her before the war, she said. Before Bletchley. Before any of this. If he taught her, he knew her, and if he knows her, he knows everything she knows. Which is why the message names him, Brennan said. The new reader wants you to know that the teacher is alive. It is an introduction, Margaret. Someone is introducing themselves. Margaret looked at the message lying on the desk between them, at the three lines of a cipher that had been built on the bones of a key used in the month Alan Pemberton went down to the lake and never came back. The same month. The same key. She had not been able to stop thinking about that all day, about the thread that ran from a drowned mathematician in 1942 to a ciphertext on her desk in 1947, thin as spider silk and strong as wire. I want to go to Norfolk, she said. Edith Crane came from a village called Wrackmore, and somebody there remembers the man who taught her. If I can find his name, I can find him. And if he is the one who wrote this, I want to ask him why he reached out to me now. Brennan studied her for a long moment. This is not your war anymore, Margaret. It never was, Margaret said. That is what the message is telling me. The long night is over, and the new one is beginning, and it is being fought by the same hands that fought the last one. I spent four years looking at the wrong fire, and the woman who set it walked free because I was looking at the ashes. I am not going to make that mistake again. She folded the message carefully and put it in her coat pocket, and she felt the weight of it there, patient as the dead. Somewhere out on the grey North Sea, a man who had taught a girl to set keys was still teaching, still writing, still reaching. And for the first time since the hangar, Margaret Chase knew exactly what she was going to do next. ---