In London, hidden deep in the city's financial center, Mansalvat Bank is small, obscure, discreet, and unimaginably wealthy. When Ellie Stanton, a penniless university graduate, is unexpectedly called to work there, the world of privileges that opens up to her seems ideal.

But the bank is not just what it seems. Soon Ellie realizes that her life belongs to her employers - who monitor her every move. Buried in the medieval underground chambers of the bank is a fiercely guarded treasure of immeasurable power, which, unbeknownst to Ellie, is directly connected to her family's history.

Willingly or not, Ellie becomes entangled in a frantic race against time, pursued by the bank and haunted by her past. Her only hope of salvation is to bring to light the secret that is buried in the underground vault. Entering there is only the beginning...