Nell Sayer authenticates old paintings. She can tell a real Caravaggio from a forgery by the pressure of a brushstroke. Seeing what is hidden beneath the surface is what she does for a living.

A contract brings her to a Boston estate. Seventy-two hours on site. Standard job.

The door locks from the outside.

He is calm. Polite. He does not threaten her. He asks her questions about Caravaggio and pours her water and watches her the way she watches canvases , slowly, systematically, looking for the thing underneath.

Nell knows she is being studied. She does not know what he is building with what he finds.

Seventy-two hours. A locked room. A man who never raises his voice. And the growing suspicion that the most dangerous thing in this room is not him.

It is how fast she is getting used to him.

The price of losing is higher than she thinks.