Edward Johnston, Regius Professor of History at Yale, squinted as the helicopter thumped by overhead.  It was heading south, toward Domme, where there was a landing field.  Johnston glanced at his watch and said, "Let's continue, Chris."

"Okay," Chris Hughes said.  He turned back to the computer mounted on the tripod in front of them, attached the GPS, and flicked the power button.  "It'll take me a minute to set up"

Christopher Stewart Hughes was one of Johnston's graduate students.  The Professor - he was invariably known by that name - had five graduate students working on the site, as well as two dozen undergraduates who had become enamored of him during his introductory Western Civilization class.

It was easy, Chris thought, to become enamored of Edward Johnston.  Although well past sixty, Johnston was broad-shouldered and fit; he moved quickly, giving the impression of vigor and energy.  Tanned, with dark eyes and sardonic manner, he often seemed more like Mephistopheles than a history professor.

Yet he dressed the part of a typical college professor: even here in the field, he wore a button-down shirt and tie every day.  His only concession to field work were his jeans and hiking boots.  What made Johnston so beloved by his students was the way he involved himself in their lives: he fed them at his house once a week; he looked after them; if any of them had a problem with studies, or finances, or family back home, he was always ready to help solve the difficulty, without ever seeming to do anything at all.

Chris carefully unpacked the metal case at his feet, removing first a transparent liquid crystal screen, which he mounted vertically, fitting it into brackets above the computer.  Then he restarted the computer, so that it would recognize the screen.

"It'll just be a few seconds now," he said.  "The GPS is calibrating."

Johnston just nodded patiently, and smiled.

Chris was a graduate student in the history of science - a bitterly controversial field - but he neatly sidestepped the disputes by focusing not on modern science, but on medieval science and technology.  Thus he was becoming expert in techniques of metallurgy, the manufacture of armor, three-field crop rotation, the chemistry of tanning, and a dozen other subjects from the period.  He had decided to do his doctoral dissertation on the technology of medieval mills - a fascinating, much-neglected area.

And his particular interest was, of course, the mill of Sainte-Mère.

Johnston waited calmly.

Chris had been an undergraduate, in his junior year, when his parents were killed in an automobile accident.  Chris, an only child, was devastated; he thought he would drop out of school.  Johnston moved the young student into his house for three months, and served as a substitute father for many years afterward, advising him on everything from settling his parents' estate to problems with his girlfriends.  And there had been a lot of problems with girlfriends.

In the aftermath of his parents' death, Chris had gotten involved with many women.  The subsequent complexity of his life - dirty looks in a seminar from a jilted lover; frantic midnight calls to his room because of a missed period, while he was in bed with someone else; clandestine hotel-room meetings with an associate professor of philosophy who was in the midst of a nasty divorce - all this became a familiar texture to his life.  Inevitably his grades suffered, and then Johnston took him aside, spending several evenings talking things through with him.

But Chris wasn't inclined to listen; soon after, he was named in the divorce.  Only the Professor's personal intervention prevented him from being expelled from Yale.  Chris's response to this sudden jeopardy was to bury himself in his studies; his grades swiftly improved; he eventually graduated fifth in his class.  But in the process he became conservative. Now at twenty-four, he tended toward fussiness, and stomach trouble.  He was reckless only with women.