On the Isle of Iona in a Christian monastery, Aeden and his brethren work to transcribe the Gospel of John. Together, they create parchment and intricate designs, illuminating them with fine inks and gold leaf. Their meticulous hands and virtuous hearts transcribe God's word.
Unfortunately, the monastery is not immune to the barbarians invading from the north: the Vikings. Fearful for their precarious position and important work, the Abbot Father Cellarch enlists the help of a Viking king who values Christianity. King Blachmac pledges protection, leaving his daughter Osla in their care as the raids continue.
Osla and Aedan, drawn to one another, develop a friendship as work continues on the Gospels. During this tumultuous time, the Book of John is completed amid stress, love, and accusations of murder. These events bring the star-crossed lovers closer. Together, they save the abbey and their precious work.
Scriptorium is Aedan, Osla, and their brethren's story of courage, where pure hearts triumph over barbaric evils. Little did they know their work would become Ireland's finest national treasure: The Book of Kells.