Trepper group In 1939, Gruber was recruited by
Leopold Trepper who was the leader of a Soviet espionage group in Europe. On the way back, Gruber escorted
Sophia Poznańska back to Brussels.
Arrest Rajchmann was arrested by Abwehr officer, Harry Piepe, on the 2 September 1942. Rajchmann also decided to cooperate with the Abwehr resulting in his betrayal of his mistress, who was arrested in Paris on the 12 October 1942 at the Cafe de la Paix. Gruber immediately decided to cooperate with the Abwehr, in an attempt to avoid
intensified interrogation, i.e. torture. Together with Rajchmann, she enthusiastically collaborated in betraying several agents in the network both in Brussels and later in Paris, that surprised German officials. She admitted the existence of a Soviet agent
Anatoly Gurevich and his probable location, as well as exposing several members of the Trepper espionage network in France. As a member of the Red Orchestra, it would have been expected that she and Rajchmann would have been executed. However, the fact that she survived was not due to their service to the Sonderkommando, but due to a Gestapo officer, Rudolf Radke, who became friendly with Gruber, saving Gruber from death on the pretext that the investigation was not completed. After being released, Gruber was allowed to return to Brussels. ==Political attack==