This book explores the absent and missing in debates about science and security. Through varied case studies, including biological and chemical weapons control, science journalism, nanotechnology research and neuroethics, the contributors explore how matters become absent, ignored or forgotten and the implications for ethics, policy and society.The chapter 'Sensing Absence: How to See What Isn't There in the Study of Science and Security' is open access under a CC BY 4.0 license via link.springer.com.