In December 1942 Agazarian arrived in Paris to join the newly formed Prosper network and was joined later by his wife Francine. He occasionally worked for Henri Dericourt, a former French Air Force pilot whose job was to find landing grounds and arrange receptions for SOE agents arriving by air. He began to question Dericourt's loyalty and reported to London his own and other agents' suspicions.
Agazarian became known to the Gestapo and there were several occasions when he narrowly escaped arrest.
Circuit leader Francis Suttill considered his (Agazarian's) continued presence to be a security risk. On June 16, 1943 he was returned to England and conveyed his fears concerning Dericourt to Nicholas Bodington and Maurice Buckmaster, who were nevertheless unconvinced.
Official concerns about the Prosper Network arose when Noor Inyat Khan lost contact with the group and reported the fact to Baker Street in London. The concerns gained weight when SOE's head of codes and ciphers Leo Marks, became convinced that Gilbert Norman, the group's wireless operator, was working under German control.
Bodington, still unconvinced, persuaded Buckmaster to allow him and Agazarian to return to France and investigate, which they did on July 22, 1943.
Bodington, via Baker Street, arranged a meeting with Gilbert Norman at a pre-arranged address in the rue de Rome near Gare St-Lazare, but it was Agazarian, not Bodington who went to the meeting.
The concerns about the Prosper network then proved to be correct. German forces were waiting and Agazarian was arrested. Three members of the network, courier Andrée Borrel, the leader Francis Suttill and wireless operator Gilbert Norman, had been in custody since June 23rd and Norman's transmissions had indeed been made by the Germans.
The arrest of Agazarian, who knew a great deal about the Prosper network, was a massive coup for the Germans. He endured torture for six months at Fresnes prison and was then moved to Flossenbürg concentration camp. After being kept there in solitary confinement, Agazarian was executed on March 29, 1945.