The police have finally caught the evil murderer Sir Mason Green. The third casket and whatever treasure it contains can remain a secret just as the Fraternity wished. Gerald can relax and enjoy his billions. Or can he? At his trial, Green drops dead in the dock. Forensics show he was poisoned by a dart - and Gerald's DNA is on the blowgun. Then a mysterious cat woman steals the ruby, the key to the third casket. A mysterious woman with a store of poison darts, who happens to be Sir Mason Green's niece, Charlotte. Now Gerald is on the run, with Ruby and Sam, wanted for murder.

Can they beat Charlotte to the ruby casket and prove that she killed Green? It's a quest that takes them to caverns beneath the island castle of Mont St Michel in France, locked rooms in the Vatican and the ancient hidden city of Delphi in Greece to discover the secret of the three caskets and the great power they hold.