Enigma

1

    CAMBRIDGE IN THE fourth winter of the war: a ghost town.
    A ceaseless Siberian wind with nothing to blunt its edge for a thousand miles whipped off the North Sea and swept low across the Fens. It rattled the signs to the air-raid shelters in Trinity New Court and battered on the boarded-up windows of King's College Chapel. It prowled through the quadrangles and staircases, confining the few dons and students still in residence to their rooms. By mid-afternoon the narrow cobbled streets were deserted. By nightfall, with not a light to be seen, the university was returned to a darkness it hadn't known since the Middle Ages. A procession of monks shuffling over Magdalene Bridge on their way to Vespers would scarcely have seemed out of place.
    In the wartime blackout the centuries had dissolved.
    It was to this bleak spot in the flatlands of eastern England that there came, in the middle of February 1943, a young mathematician named Thomas Jericho. The authorities of his college, King's, were given less than a day's notice of his arrival—scarcely enough time to reopen his rooms, put sheets on his bed, and have more than three years' worth of dust swept from his shelves and carpets. And they would not have gone to even that much trouble, it being wartime and servants so scarce—had not the Provost himself been telephoned at the Master's Lodge by an obscure but very senior official of His Majesty's Foreign Office, with a request that 'Mr Jericho be looked after until he is well enough to return to his duties'.
    'Of course,' replied the Provost, who couldn't for the life of him put a face to the name of Jericho. 'Of course. A pleasure to welcome him back.'
    As he spoke, he opened the college register and flicked through it until he came to: Jericho, T. R. G.; matriculated, 1935; Senior Wrangler, Mathematics Tripos, 1938; Junior Research Fellow at two hundred pounds a year; not seen in the university since the outbreak of war.
    Jericho ? Jericho ? To the Provost he was at best a dim memory, a fuzzy adolescent blob on a college photograph. Once, perhaps, he would have remembered the name, but the war had shattered the sonorous rhythm of intake and graduation and all was chaos—the Pitt Club was a British Restaurant, potatoes and onions were growing in the gardens of St John's . . .
    'He has recently been engaged upon work of the gravest national importance,' continued the caller. 'We would appreciate it if he were not disturbed.'
    'Understood,' said the Provost. 'Understood. I shall see to it he is left alone.'
    'We are obliged to you.'
    The official rang off. 'Work of the gravest national importance', by God . . . The old man knew what that meant. He hung up and looked thoughtfully at the receiver for a few moments, then went in search of the domestic bursar.
    A Cambridge college is a. village, with a village's appetite for gossip—all the keener when that village is nine-tenths empty—and the return of Jericho provoked hours of analysis among the college staff.
    There was, for a start, the manner of his arrival—a few hours after the call to the Provost, late on a snowy night, swaddled in a travelling rug, in the back of a cavernous official Rover driven by a young chauffeuse in the dark blue uniform of the Women's Royal Navy. Kite, the porter, who offered to carry the visitor's bags to his rooms, reported that Jericho clung to his pair of battered leather suitcases and refused to let go of either, even though he looked so pale and worn out that Kite doubted he would make it up the spiral staircase unaided.
    Dorothy Saxmundham, the bedder, saw him next, when she went in the following day to tidy up. He was propped on his pillows staring out at the sleet pattering across the river, and he never turned his head, never even looked at her, didn't seem to know she was there, poor lamb. Then she went to move one of his cases and he was up in a flash—'Please don't touch that, thank you so much, Mrs Sax, thank you'—and she was out on the landing in a quarter of a minute.
    He had only one visitor: the college doctor, who saw him twice, stayed for about fifteen minutes on each occasion, and left without saying a word.
    He took all his meals in his room for the first week—not that he ate very much, according to Oliver Bickerdyke, who worked in the kitchens: he took up a tray three times a day, only to take it away again an hour later, barely touched. Bickerdyke's great coup, which led to at least an hour of