When prestigious art conservator Grace Montgomery is commissioned to restore a damaged 18th-century painting from a Scottish Masonic temple, she discovers something extraordinary: Hidden beneath the surface is an earlier work depicting the twelve tribes of Israel arranged in an alchemical mandala, with Hebrew inscriptions from Exodus describing the Tabernacle's construction as a formula for spiritual transformation.

Her discovery attracts the attention of Ian MacLeod, a Scottish theologian and Mason who's spent years researching the connection between the Tabernacle, alchemy, and Masonic architecture. Together they uncover evidence of a covenant made by Christian alchemists and early Freemasons to preserve biblical wisdom that mainstream Christianity had forgotten-wisdom about humanity's divine nature and destiny.

But when Grace's former mentor is murdered for possessing similar knowledge, she and Ian realize they're not just uncovering history-they're completing a three-century quest that others will kill to stop. Racing through Highland castles, ancient abbeys, and Masonic halls, they must decode the "Emerald Covenant" while confronting their deepest fears and discovering that sometimes God's greatest treasures are found in the furnace of affliction... and in the arms of the beloved He provides.