The article treats some general features of the mission of Theophilos the Indian to South Arabia and East Africa in the middle of the IV cent. AD. One of the places where Christian churches were built up is called Persian emporium, which could be identified with ancient port Qana’. The location of Qana’ fits the description of Philostrgius as lying «in another part of Ḥimyar» and the information of the Classical geographers as lying close to Persia and having strong contacts with Persian markets. The «Inner India» in the account of Philostorgius is to be identified with the island of Suquṭrā’. Thus the return of Theophilos to «Inner India» from the South Arabian mainland additionally suggests to the identification of the island of Dibos with modern Suquṭrā’. Another peculiarity of the mission of Theophilos the Indian is that he personally could be involved into the struggle between Nicean and Arian fractions the of Christian church. Namely Theophilos the Indian could deliver the order to send away Frumentius – the former bishop of Axum – from the court of ‘Ēzānā.