Paris, 1277. When logic professor Guillaume de Montfort finds his mentor dead, clutching a mysterious manuscript covered in geometric patterns, he uncovers a secret that could shatter medieval society: consciousness itself shapes reality, and the architecture of Notre-Dame Cathedral was designed to prove it.

As scholars begin dying and strange entities manifest in Paris's streets, Guillaume must race against time to decode his father's work and prevent ancient geometric beings from using Notre-Dame's Easter Mass to collapse all possible realities into a single, simplified pattern. Aided by the enigmatic Sister Héloïse and scholars from different faiths, he faces a choice that will affect not just this world, but all possible worlds where consciousness seeks to understand itself.

"The Heretic's Codex" is a metaphysical thriller that combines historical mystery with philosophical speculation, exploring what happens when medieval minds confront the infinite possibilities of human consciousness.