Lupin & co. attempt to steal two face plates from millionare Michael Sizuki, thinking that they will lead to an ancient treasure when brought together. However, it soon becomes apparent that there is more behind the plates then meets the eye. 

(Source: ANN)

Two jewels are the key to the ancient treasure of Yaobikuni. But legend has it that the only person who can find the treasure is one who can walk the path of death.

And why is Lupin interested? This is the one treasure his grandfather sought but did not steal.

(Source: AniDB)