In Aunt Tilley's house, Kyla and E.B. investigate random objects in the file drawers they inherited from Great Aunt Hermione that show how history connects to who we are and how we live now. Behind the label "To fill or not to fill?" is an old hardhat that takes E.B. to a construction site where excavators are digging a new building foundation; the removed soil which will become landfill in another area. A picture shows the old Toronto Harbour Commission building at the waterfront, but today it's several blocks from the lake. Kyla learns why from an archives expert. Infill is the answer. And a bird migration map leads them to the Leslie Street Spit, another land form created by construction waste infill which nature turned into a wildlife habitat. Infill is used to create more land all over the world.