During the 1950s and 1960s Marsh made many appearances on British and American television, including an episode of "The Twilight Zone" called "The Lonely" (1959), in which she portrayed a lifelike robot; "The Moon and Sixpence" (1959) opposite Laurence Olivier and Denholm Elliott; "The Wonderful World of Disney" (1961); "Gideon's Way" (1965); "I Spy" (1967); in four episodes of "The Saint" (1964–1968); and one episode of "UFO" ("Exposed", 1970). She was also a regular in the ITV series "The Informer" (1966–67) starring Ian Hendry.