Federal investigators from Delaware closed the books on a decades-old international mystery this month at a ceremony in Rome.

The crime involved daring forgeries at the Vatican, international smugglers, a secretive world of wealthy book collectors, and long-lost 15th-century bound editions of letters Christopher Columbus sent from the New World.

In libraries from Barcelona to the Vatican, thieves had taken four of the last original editions of these Christopher Columbus letters known to exist, replacing them with clever forgeries that took decades to discover.