At the start of the performance, the attendees are asked not to take any photos or videos.

A square of 200 cm by 200 cm is plotted on the wall with masking tape. The enclosed space is then painted with the same whitewash the walls were previously painted with. When the painting is finished, the masking tape is removed and the floor is cleaned of any spilled paint.
It is still possible to distinguish the square, but as the paint dries, the square will fade and merge with its surroundings.
The attendees leave when all traces have disappeared.