Maverick American biologist Dr Roberta Ryder receives a mysterious letter from her friend Claudine and travels to Paris to see her, only to learn of her shocking death. Before she knows it, Roberta becomes the target of ruthless men with a deadly agenda that only the letter can unmask. Ben Hope, now trying to retire, finds his life turned upside down by Roberta's arrival. In a franctic race to Paris to uncover the mystery of Claudine's research, they uncover a global conspiracy that will claim the lives of millions of people ... unless Ben can stop it.