The Hollow Needle is a novel by Maurice Leblanc featuring the adventures of the gentleman thief, Arsène Lupin. Arsène Lupin is opposed this time by Isidore Beautrelet, a young but gifted amateur detective, who is still in high school but who is poised to give Arsène Lupin a big headache. In the Arsène Lupin universe, the Hollow Needle is the second secret of Marie Antoinette and Alessandro Cagliostro, the hidden fortune of the kings of France, as revealed to Arsène Lupin by Josephine Balsamo in the novel The Countess of Cagliostro (1924). The Mystery of the Hollow Needle hides a secret that the Kings of France have been handing down since the time of Julius Caesar... and now Arsène Lupin has mastered it. The legendary needle contains the most fabulous treasure ever imagined, a collection of queens' dowries, pearls, rubies, sapphires and diamonds... the fortune of the kings of France.