Bhakta Prahlada is about Prahlada (Roja Ramani,) Lord Vishnu's staunch devotee, and Hiranyakashipu (S.V. Ranga Rao,) his father. Hiranyakashipu is determined to dissuade his son from worshipping Lord Vishnu, as the Lord killed his brother, Hiranyaksa. To prevent Prahalad's devotion, Hiranyakashipu is willing to go to any extent.
Whether he is successful or not forms the rest of the story.