Enigma

million.
    He did the plugging first. Short lengths, of corded, chocolate-coloured flex, tipped at either end by brass plugs sheathed in bakelite that sank with satisfying precision into the lettered sockets: C to X, A to Z ...
    Next he lifted the Enigma's inner lid, unlocked the spindle, and slid off the three rotors that were already loaded. From a separate compartment he withdrew the two spares.
    Each rotor was the size and thickness of an ice-hockey puck, but heavier: a code wheel with twenty-six terminals—pin-shaped and spring-loaded on one side, flat and circular on the other—with the letters of the alphabet engraved around the edge. As the rotors turned against one another, so the shape of the electrical circuit they completed varied. The right-hand rotor always moved on a letter each time a key was struck. Once every twenty-six letters, a notch in its alphabet ring caused the middle rotor also to move on a place. And when, eventually, the middle rotor reached its turnover position, the third rotor would move. Two rotors moving together was known at Bletchley as a crab; three was a lobster.
    He sorted the rotors into the order of the day—III, V and IV—and slipped them on to the spindle. He twirled III and set it at the letter G, V at A and IV at H, and closed the lid.
    The machine was now primed just as its twin had been in Smolensk on the evening of 4 March.
    He touched the keys. He was ready.
    The Enigma worked on a simple principle. If, when the machine was set in a particular way, pressing key A completed a circuit that illuminated bulb X, then it followed—because electric current is reciprocal—that, in the same position, pressing key X would illuminate bulb A. Decoding was designed to be as easy as encoding.
    Jericho realised quite quickly that something was going wrong. He would type a letter of the cryptogram with his left index finger and with his right hand make a note of the character illuminated on the display panel. T gave him H, R gave him Y, X gave him C .. . This was no German he recognised. Still, he went on in the increasingly desperate hope it would start to come right. Only after forty-seven letters did he give up.
    HYCYKWPIOROKDZENAJEWICZJPTAKJHRUTBPYSJMOTYLPCIE
    He ran his hands through his hair.
    Sometimes an Enigma operator would insert meaningless padding around proper words to disguise the sense of his message, but never this much, surely? There were no proper words that he could discern hidden anywhere in this gibberish.
    He groaned, leaned back in his chair and stared at the flaking plaster ceiling.
    Two possibilities, each equally unpleasant.
    One: the message had been super-enciphered, its plaintext scrambled once, and then again to make its meaning doubly obscure. A time-consuming technique, usually reserved for only the most secret communications.
    Two: Hester had made a mistake in transcription—had got, perhaps, just one letter wrong—in which case he could sit here, literally for the rest of his life, and still he would never make the cryptogram disgorge its secrets.
    Of the two explanations, the latter was the more likely.
    He paced around his cell for a while, trying to get some circulation back into his legs and arms. Then he set the rotors back at GAH and made an attempt to decipher the second message from 4 March. The same result:
    SZULCJK UKAH
    He didn't even bother with the third and fourth but instead played around with the rotor settings—GEH, CAN, CAH—in the hope she might simply have got one letter wrong, but all the Enigma winked at him was more gobbledygook.
    Four in the car. Hester in the back seat next to Wigram. Two men in the front. The doors all locked, the heater on, a stench of cigarette smoke and sweat so strong that Wigram had his paisley scarf pressed delicately to his nose. He kept his face half-turned from her all journey and didn't say a word until they reached the main road. Then they pulled across the white lines to overtake another car and their driver switched on a police bell.
    'Oh, for Christ's sake, Leveret, cut it out.'
    The noise stopped. The car swerved left, then right. They jolted down a rutted track and Hester's fingers sank deeper into the leather upholstery as she strained to avoid toppling into Wigram. She hadn't spoken, either—it was her single, token gesture of defiance, this silence. She was damned if she was going to show her nerves by babbling like a girl.
    After a couple of minutes they stopped somewhere and