Helfeld and Lepidus were members of the Latvian Socialist Party responsible for smuggling revolutionary literature into Russia. Both had been living with Lepidus's brother Paul in Paris in 1907 when Paul was killed by the premature detonation of the bomb he was carrying to assassinate the president of France, Armand Fallières. They fled France to north London, where they became members of a small group of Latvian agitators.