With the publication of the Ophthalmographia in 1632, the Amsterdam physician Vopiscus Fortunatus Plempius sheds new light on the age-old question of how seeing works. His answer is an invitation to experiment: Enter with me into a darkened room and prepare the eye of a freshly slaughtered cow. He emphasizes that anyone may carry out this experiment, at home, "demanding little effort and expense." "And you, standing in the darkened room, behind the eye, shall see a painting that perfectly represents all objects from the outside world," promises Plempius. In the short film In Waking Hours we see historian Katrien Vanagt - who studied the Latin writings of this Plempius - cloaked in the skin of a 21st-century disciple of Plempius. Her cousin, filmmaker Sarah Vanagt, is there and captures how this modern "Plempia" meticulously follows her teacher's instructions. Thus, in a dark kitchen in Brussels, they become witnesses at the birth of images upon the eye.