Book 4 in the Christie and Agatha's Detective Agency series!"If you want to see your cousin again, come to the old quay at seven tomorrow night, alone.Be prepared to be married. Do not involve the police."A relaxing break on the French Riviera becomes a dramatic investigation when famous physicist, Irène Curie, receives a ransom note demanding her hand in marriage.What’s more, Christie and Agatha’s friend has been kidnapped!Can the twins find out who is behind the ransom note and save both Auguste and Miss Curie?About the Christie and Agatha's Detective Agency series:It’s not easy growing up in the 1920s.While Christie can usually be found up a tree or trying a spot of amateur engineering, her shy twin Agatha buries her nose in books and dreams of being a writer.The pair couldn’t be more different. But when a scientific discovery goes missing, they find that together they make a winning combination and Christie and Agatha’s Detective Agency is born.Join the twin detectives as they solve thrilling mysteries all over the world!