Long ago, a thousand men and women abandoned their lives to follow a stranger. Now their legacy threatens modern existence . . . In 530 BC a mysterious ship appeared off the rainy shores of Croton in what is now Italy. After three days, a man disembarked to address the curious and frightened crowd that had gathered. He called himself Pythagoras. Exactly what he said that day is unknown, but afterwards a thousand men and women abandoned their lives and families to follow him. Over the centuries they became a secret society of powerful individuals safeguarding the teachings of one of history's most brilliant mathematicians. But now, triggered by a brutal murder in Chicago, the brotherhood erupts into civil war, and a young woman finds herself at the centre of ancient revelations that could not only become instruments of terror but could jeopardise civilisation itself . . .