[1] It tells the story of the three sons of Connall ua Corra, a landowner of Connacht, who had made a bargain with the Devil before their birth.
[2] The three sons grew up to become leaders of a notorious gang of bandits who targeted the churches of the province, until they were struck by a vision and repented their ways.
The penitent three proceeded to the monastery of St. Finnian of Clonard, who instructed them to repair every church they had destroyed.
As a final act of contrition, on the advice of St. Coman of Kinvara, the keeper of the last church they repaired, the three brothers set out on an Atlantic Ocean voyage on a small boat (a currach), accompanied by five others (a bishop, a priest, a deacon, a musician and the craftsman who built the boat).
They then proceeded back to Ireland, and related the story of their adventures, where it was eventually written down in the form of a poem.