It’s been described to me: the way the light changes in the window in the background. But no matter how I concentrate, and as if by a will of its own, my focus is drawn into the picture, moving along the wainscoting, over the gray walls, toward the book on the table, the cut of the chair-back, then resting always for a moment on the luminous nape of the woman in the black dress, who sits turned away and with her head bowed. Exactly at this moment, either the sunlight suddenly changes quality, or someone’s shadow hastens past the window in the background. You hardly notice it, and when you look, it’s already too late.