According to the "Vita", Fridolin belonged to a noble family in Ireland, and at first was a missionary there. Afterwards crossing to France, he came to Poitiers, where in answer to a vision, he sought out the relics of Saint Hilarius, and built a church for them. Saint Hilarius subsequently appeared to him in a dream, and commanded him to proceed to an island in the Rhine, in the territories of the Alamanni. In obedience to this summons, Fridolin approached "emperor" Clovis, who granted him possession of the still unknown island, and thence proceeded through "Helion", Strasbourg and Coire, founding churches in every district in honour of Saint Hilarius.