Sean Kilgore, born with the same distinctive birthmark as his father, grandfather, and great-grandfather, has no idea that he belongs to the world, not just his parents. Months later after a car accident robs him of his parents and his history, little Sean is adopted by his father's colleague. Sean Kilgore is now Sean Brennan. As Sean grows older and learns he is adopted, he cannot escape the belief that his triangular birthmark has significance. Yet his attempts at discovering what it means only deepen the mystery.

Years later, Sean feels like a stranger in his own life, encumbered by a restlessness that beckons him into the unknown. Seeking to escape a past marred with disappointment and tragedy, Sean leaves a life of certainty behind and travels from Toronto to Kabul to London and finally to Janus, an uncharted island in the North Atlantic, where he soon discovers a peaceful society, committed to remaining isolated from the world. As Sean immerses himself in a new life, he is unaware that beneath the peaceful charm lies a hidden truth: the island's enigmatic leader, a beautiful woman, and The Spirit know more about him than he does.

The Mark of Janus is the compelling tale of one man's journey to fulfill a purpose two centuries in the making as the future of the world waits.