A vision comes to seventeen-year-old Rosamund. "I dreamed on Shrove Tuesday I would find a most sacred relic." To rescue her village from sin and famine, she is sent by the abbot to Constantinople to translate a relic "of divine power and uttermost brilliance." She disguises herself as a religious pilgrim and embarks on a perilous quest in medieval thirteenth-century Aquitaine.

"It doesn't matter to me how you learn this story," Jesse writes in his Internet diary. "Only that you do." In Los Angeles at the beginning of the twenty-first century, the world is succumbing to ecological and biological disaster. It is the onset of an Ice Age. Nations are gone; city-states endure. Jesse is a cyber-savvy, BASE-jumping ("to put the nerve back in Nirvana") seventeen-year-old on a quest to find his distant, mysterious father.

Rosamund sails on a crusader ship from Venice, is an unwilling witness to the sacking of Zara, becomes a legend--a saint in the making. Jesse travels from LA to the Arizona desert, from Africa to the shores of Santa Barbara, and becomes one of the richest men in the world.

Rosamund has visions of Jesse and believes God sends him. Jesse has visions of Rosamund and assumes she's a virtual babe. They soon cross an invisible framework of time to find that they are ancestor and descendant, and their journeys are connected.

Both are synesthetes, can taste "points" on their palms, see F-sharp as green, and have photographic recall. Both are impulsive, and given to high-voltage epiphanies. Both plunge into questionable love affairs. Both become parents, both have to choose between their original quest and saving their children. And both come to realize they are part of a very old story.