Lupin, Who Killed Lupin

Fujiko dies in Lupin's arms. Lupin flips out, but it's all a put-up job: having heard, at the last, the location of Lupin's most precious treasure, Fujiko teams up with the villain Helgar. An extremely angry Lupin takes off after them, but an almighty Minotaur defense system awaits at the hiding place, on the island of Crete. Helgar himself developed this transforming weapon. What is Lupin's treasure?