The Treasure of Pompeii has lain forever untouched because it is guarded by countless venomous snakes deep inside a convent. Lupin acquires an antivenom set from the Red Cross, and promptly makes his own attempt on the treasure. Lucia, a girl who has numerous loves for a nun, plots to take the treasure for herself while helping Lupin. She wants to be happy, you see. What is the treasure, really?