Many conversations ended bitterly, with her mother saying, ‘No one suffers like I suffer,’ making Shadia droop. At night her mother sobbed in her sleep, noises that woke Shadia and her sisters.

No, on the long-distance line, there was no space for her worries. Talk about the Scottish weather. Picture Fareed, generously perspiring, his stomach straining the buttons of his shirt. Often she had nagged him to lose weight with no success. His mother’s food was too good – his sisters were both overweight. On the long-distance line, listen to the Khartoum gossip as if listening to a radio play.

On Monday, without saying anything, Bryan slid two folders across the table towards her as if he did not want to come near her, did not want to talk to her. She wanted to say, ‘I won’t take them till you hand them to me politely.’ But smarting, she said, ‘Thank you very much.’ She had manners. She was well brought up.

Back in her room, at her desk, the clearest handwriting she had ever seen. Sparse on the pages, clean. Clear and rounded like a child’s, the tidiest notes. She cried over them, wept for no reason. She cried until she wetted one of the pages, stained the ink, blurred one of the formulas. She dabbed at it with a tissue but the paper flaked and became transparent. Should she apologise about the stain? Say that she was drinking water, say that it was rain? Or should she just keep quiet and hope he wouldn’t notice? She chided herself for all that worry. He wasn’t concerned about wearing the same shirt every day. She was giving him too much attention thinking about him. He was just an immature and closed-in sort of character. He probably came from a small town; his parents were probably poor, low class. In Khartoum, she never mixed with people like that. Her mother liked her to be friends with people who were higher up. How else were she and her sisters going to marry well? She must study the notes and stop crying over this boy’s handwriting. His handwriting had nothing to do with her, nothing to do with her at all.

Understanding after not understanding is fog lifting, is pictures swinging into focus, missing pieces slotting into place. It is fragments gelling, a sound vivid whole, a basis to build on. His notes were the knowledge she needed, the gaps. She struggled through them, not skimming them with the carelessness of incomprehension, but taking them in, making them a part of her, until in the depth of concentration, in the late hours of the nights, she lost awareness of time and place and at last when she slept she became epsilon and gamma and she became a variable making her way through discrete space from state i to state j.