It’s quiet. The afternoon sky is draped in a blanket of clouds and a breeze weaves its way through the trees. Down a winding dirt path in the woods of Waltham, Massachusetts, is a clearing peppered with hundreds of small, gray slabs of concrete. They sink into the earth as if pulled down by invisible hands. These uneven stumbling stones serve as crass grave markers for the hundreds of people who died in two nearby institutions for people with disabilities. The cemetery is shared by the Metropolitan State Hospital, a…