[3] During the interwar period and early World War II, Schneider was a core member of a Soviet espionage group.
She worked as a principal courier for the groups that were associated with the Comintern agent, Henry Robinson in the late 1930s in France and later the Soviet GRU officer, Konstantin Jeffremov in Belgium and the Low Countries, in the early 1940s.
[3] In 1936, while the couple were living in Brussels, they were recruited as Soviet agents of the Red Army Intelligence (GRU) to work as couriers.
[11] In November 1936, Harry II introduced Schneider to Ernest David Weiss in South Kensington, London.
[12] During that period from 1936 to 1939, Schneider visited Weiss at his home in South Kensington several more times[13][14] as well as working as a courier in France, Netherlands, Switzerland, Germany.
[3] From 1939 to 1942, Germaine Schneider and her husband worked as a couriers for a Soviet espionage network that operated in the Low Countries that became known as the Red Orchestra.
Her funeral was attended by Maurice Aenis-Hanslin, a Swiss communist and commercial director who was an agent of the network run by Henry Robinson.