Paris, 1923: a young American photographer, Muriel Ross, finds herself documenting antiques that US Senator Tom Bryan has travelled to France to acquire. At first revelling in the freedom Paris affords, events take a dangerous turn when Muriel intuitts that Senator Bryan is on a mission far more momentous, and potentially deadly, than a mere shopping trip.
Asked to photograph an astonishing artefact – a piece of the True Cross on which, legend has it, Christ was crucified – Muriel is deeply moved. When rumours surface that a second fragment has been unearthed in Constantinople, she becomes enmeshed in a covert international alliance dedicated to authenticating this sacred relic . . . and protecting it from those who will stop at nothing to steal and discredit it.