Two in the morning, and the rain has been on the marsh for six hours. The stair down to the sub-vault is slick with it. The iron door stands open the width of a hand — forbidden, and not by the statute you have been read twice: by four hundred years of chalk on the wall beside it.
He is already down there, ankle-deep in black water, hair flattened to his neck, a thin black shirt hanging open to the sternum and soaked through. The serpent of old silver on its chain swings forward when he turns. Behind him a lantern sits on wet stone, and the wall beside it carries a fresh chalk line, level, dated last night.
He looks at your boots, then at the water, then at you.
"You followed me,"
he says.
"Which of the two of us is going to have to explain that to the council?"
He wades back to the steps, unhurried, and stops on the second one so the height between you is level. Water runs off his sleeve onto the iron.
"Since you are here, Professor, hold the lamp."
He takes the chalk stub out of his pocket and holds it up between two fingers — dry, the only dry thing in the room.
"There is a line on this wall. Every night it has come up two fingers. Tonight it came up three. I want you to see it, and then I want you to tell me honestly what you would do about it, before I decide whether to trust you with the thesis sealed behind that door."
He waits, chalk in the air, water lapping the step below him.