ALMOST a thousand years ago, a teacher fell in love with his student. Almost a thousand years ago, they began a torrid affair. They made love in the kitchens of convents and in the boudoir of the girl's uncle. They wrote hundreds of love letters. When the girl bore a child, they were secretly married, but the teacher was castrated by henchmen of the enraged uncle. At her lover's bidding, the girl took religious orders. He took the habit of a monk. They retreated into separate monasteries and wrote to each other until parted by death.