In 1637, the French mathematician Pierre de Fermat scrawled a note in the margin of a book about an enigmatic theorem. He also neglected to record his proof elsewhere. Thus began a search for the Holy Grail of mathematics, a search that didn't end until 1994, when Andrew Wiles published a 150-page proof. But the proof was burdensome, overlong, and utilized mathematical techniques undreamed of in Fermat's time, and so it left many critics unsatisfied, including young Ranjit Subramanian, a Sri Lankan with a special gift for mathematics and a passion for the famous "Last Theorem".

When Ranjit writes a three-page proof of the theorem that relies exclusively on knowledge available to Fermat, his achievement is hailed as a work of genius, bringing him fame and fortune. But it also brings him to the attention of the National Security Agency and a shadowy United Nations outfit called Pax per Fidem, or Peace Through Transparency, whose secretive workings belie its name. Suddenly Ranjit and his wife, Myra de Soyza, an expert in artificial intelligence, find themselves swept up in world-shaking events, his genius for abstract mathematical thought put to uses that are both concrete and potentially deadly.