In a museum in Europe, there is a ring shaped like a Lion's claw, clasping a small rough diamond. During the middle ages, this strange ring was known as the 'Ring of Death'. The year is 1500, and the Duke of Arbeno has secretly conspired with other nobles in a plot to overthrow the powerful and treacherous Caesar Borgia. All is ready, until suddenly Borgia visits the home of one of the conspirators, who mysteriously dies later that night. His wife Maria is haunted by the memory of a ring, shaped like a Lion's claw, clasping a small rough diamond...