Res Nullius explores the coexistence of humans and wildlife in the heart of Brussels and examines the way we live in the city. By following the trail of a wild boar spotted in a park, the film reveals an often-overlooked reality: the city is a living ecosystem, at the crossroads of issues relating to biodiversity, urban planning and social justice. Through the perspectives of those working on the ground, it offers a committed and political reflection on urban development and its impact on living organisms.