To Sister Beatrice, a priestess of the global Order of St. Michael, the cloud of tiny white particles is a message from God.  To Johann Eberhardt, a German systems engineer, it is an anomaly of physics.  But to the Rama society, it may; be the long-awaited proof of nonhuman intelligence.  On Mars, Johann and Beatrice will meet, drawn together by a fabulous account of a vast city lost beneath the red planet's harsh landscape.  Joined by none Martian colonists, the mystic and the skeptic will board a strange craft that will hurtle them toward the truth behind the mysterious bright messergers and a startling journey into the heart of the unknown.