Lupin is given a half diamond in a act of good faith by his old friend the crime boss Doruune. He is told the jewel is part of a key to an ancient Morocco treasure of immeasurable value. Keen to get to the treasure, Lupin catches the first train to Morocco, with the ever determined Inspector Zenigata in hot pursuit. However before the Inspector can arrest him, the train is attacked by a team of highly skilled assassins, all seemingly after Lupin. When he finally gets to Morocco, he finds that he is in the middle of a conflict between the local government and underground sects; all seeking Lupin, his diamond and the treasure that it leads to.