Edith’s career and collaboration with Fritz Machlup at Johns Hopkins University flourished and she began work on the growth of the firm, and studied the Hercules Powder Company. As Cold War tensions increased during the 1950s she and Penrose became involved in the defence of their friend and colleague Owen Lattimore who was named as the top Soviet spy by Senator McCarthy. The chapter covers the persecution of Lattimore, his trials, the role of Judge Luther Youngdahl, and the operation of his defence fund. Other friends of E. F. Penrose became victims of the anti-communist ‘witch hunt’, he grew increasingly disillusioned with the USA, and determined he must leave. In 1953 Edith and Penrose testified before the Senate Internal Security Subcommittee. They were also investigated by the FBI. After five years the case against Lattimore was dropped. Edith’s father died and her brother Harvey was killed in an air accident.