Joan Wilder, a thriving yet solitary romance novelist, lives in New York City alongside her beloved cat, Romeo. After completing her latest novel, she ventures out of her apartment to meet her editor and close friend, Gloria Horne. On her way, Joan is stopped by her neighbor, Mrs. Irwin, who hands her a letter containing a mysterious map sent by her recently murdered brother-in-law, Eduardo.  

While Joan is away, a man breaks into her apartment but is confronted by the building’s superintendent, whom he kills before fleeing. Upon returning home, Joan finds her apartment torn apart. To complicate matters further, she receives a desperate phone call from her sister, Elaine, Eduardo's grieving widow. Elaine has been kidnapped by antiquities smugglers—two cousins named Ira and Ralph—who demand the map as ransom. Following Elaine's instructions, Joan is thrust into an unexpected journey to the coastal city of Cartagena, Colombia, with the map in hand.