The shock came the next afternoon. As she passed through the great entrance hall, fitted up as a lounge with the heterogeneous furniture, she came across him, the solitary occupant, sitting at a table, busy with pencil and writing pad and a thick volume propped up in front of him. Her eye caught arresting symbols on the paper, then the page-heading of the book: “Rigid Dynamics.” She paused. He looked up with a laugh. “Hello, Sister!” She said, with a catch in her breath, “You’re a mathematician?” He laughed. “More or less. If they kick me out of the Army, I must go back to Cambridge and begin again where I left off.” “You must have left off rather high, if you’re reading Rigid.” He started, for no one in this wide world but a mathematical student could have used the phrase. “What the—what do you know about Rigid?” “I was at Newnham, in my young days,” she replied, “and I read mathematics. And, oddly enough, my private tutor was”—she hesitated for a second—“someone of your name.” He pushed his chair away from the table. “That must have been my father.” “John Baltazar.” “Yes, John Baltazar. One of the greatest mathematical geniuses Cambridge has produced. Good Lord! did you know my father?” “He and I were great friends.” She looked him through and through with curiously burning eyes; of which the boy was unconscious, for he said: “Fancy your reading with my father! It’s a funny old world.” Then suddenly he reflected and glanced at her critically. “But how could you? He disappeared nearly twenty years ago.” “I’m thirty-eight,” she said. “Lord! you don’t look it—nothing like it,” he cried boyishly. Nor did she. She carried a graceful air of youth, from the wave of brown hair that escaped from beneath her Sister’s cap to the supple and delicately curved figure. And her face, if you peered not too closely, was young, very pure in feature, still with a bloom on the complexion in spite of confinement in hospital wards. Her voice, too, was soft and youthful. Perhaps her eyes were a little weary—they had seen many terrible things. At the young man’s tribute she flushed slightly and smiled. But the smile died away when he added: “What was he like? I’ve often wondered, and there has been no one to tell me—no one I could have listened to. The dons of his generation are too shy to refer to him and I’m too shy to ask ’em. Do you know, I’ve never seen a picture of him even.” “He was not unlike you,” she replied, looking not at him, but wistfully down the years. “Of heavier build. He was a man of tremendous vitality—and swift brain. The most marvellous teacher I have ever met. He seemed to hold your intellect in his hands like a physical thing, sweep it clear of cobwebs and compel it to assimilate whatever he chose. A born teacher and a wonderful man.”