The Hollow Needle. A Century-Old Royal Secret Hidden Inside a Cliff, and the Student Who Won't Stop Digging

A young amateur detective stumbles onto a mystery far bigger than a simple theft: a hollow needle-shaped rock on the Normandy coast that has secretly funded the kings of France for centuries - and which Arsène Lupin has just claimed as his own private treasury. What follows is one of literature's great intellectual duels, thief against student, neither willing to back down. Widely considered Leblanc's masterpiece - the novel where Lupin faces an opponent nearly as clever as he is, and where the treasure hunt becomes as thrilling as the crime itself.