Nancy Drew becomes involved in a double mystery concerning a haunted bridge and jewel thieves.

Carson Drew takes Nancy on a cruise to Rio de Janeiro. Once on board the Emerald Queen his attention turns to the beautiful widow, Nina da Silva. The problem is, Nina happens to be Nancy's top suspect in a strange case of stolen gems. As Nancy investigates, someone tries to kill her with a poisonous spider, the cruise director is wounded by a poisoned dart meant for her, and she is stalked by a phanton hit man. But Nancy is determined not to be...