Upon returning in the late 1930s, Zalmond is alleged to have been recruited for anti-Trotsky work and was sent on several missions to Canada on behalf of Soviet intelligence.
In March 1942, Franklin met with Clarence Hiskey, Professor of Chemistry at Columbia University and a member of the CPUSA, in New York City.
As they walked to the subway, Hiskey described the progress of the research that was then being undertaken at Columbia on the atomic bomb.
Hiskey would supply Franklin with classified material until he moved to the Metallurgical Laboratory at Chicago in October 1943.
Franklin had married Rose Richter after divorcing Sylvia Callen a year earlier.