The secret will of the famous painter Raffaello suddenly disappears from the collection of the Vatican Library. Agatha and Larry immediately travel to Rome to find out who the culprit could be. They also have their relative living in Rome, uncle Algernon, who is a writing expert dealing with deciphering old texts. In this way, the cousins ​​manage to track down the thief, and a sensational discovery is also made in the process!