Originally, Fáṭimih Bagum did not accept her Son's cause unlike her brother, however she kept an open mind. She was devastated on hearing the news of the treatment of her Son, and after His martyrdom her family kept it a secret from her for nearly a whole year. After hearing the news, the distraught Fáṭimih Bagum moved to Karbilá with her closest companions in December of 1851. She did not become a believer until some time later when Bahá'u'lláh instructed two of His faithful followers, Hájí Siyyid Javád-i-Karbilá'í and the wife of Hájí 'Abdu'l-Majíd-i-Shírázi to instruct her in the principles of the Faith

In 1862 he had been appointed physician to the diplomatic delegation sent to Persia to establish relations between the newly created Kingdom of Italy and the Persian government. There in Tabriz, Lessona met Daud Khan, who told him about the new Revelation. He met often with Gobineau, who had then become the French Ambassador to Persia and the two became lifelong friends. Most of Lessona's information on the Bábi Faith came from these two sources, especially the latter. He found it difficult to get any first-hand information about the Babis, but did recognize, in 1962, that the successor to the Báb was living in Baghdad.

Lessona organized two-part conference on the Bábi movement that was held in December of 1880. The following year he published the proceedings of the conference in a small monograph called I Bábi. It was the first Italian historical testimony on the Bábí - Bahá'í Faith. [Bahá'í Tributes; Bahá'í Teachings; BW12p900]