Ethan and Ella are excited to get to Paris-they've only ever seen pictures of the Eiffel Tower! After arriving, the twins receive an email from their beloved Grandpa Harry. He tells them that there's a secret bakery near the Louvre museum-so secret, in fact, that you need a password to get inside. Lucky for the twins, their dad wants to take them to see some artwork at the Louvre. But while they're browsing paintings at the museum, alarms suddenly go off, the building is evacuated, and tons of police show up outside. A painting has been stolen! And Ethan and Ella are on the case! Can they manage to find the stolen painting and the secret bakery without giving themselves away?
When Ethan and Ella first land in Venice, they are in awe of all the canals and tiny little streets. They're especially excited to look for a five-hundred-year-old-mosaic near Calle Farnese that Grandpa Harry tells them about. While the twins are out getting gelato later that day, they notice someone looking around suspiciously as he unties a gondola from a dock. The next morning, the twins hear two gondoliers arguing, one of them accusing the other of stealing his most beautiful boat. The gondolier begs Ethan and Ella to help him find the boat. They agree, but they also tell the man that they need to get to Calle Farnese. Will the twins be able to find the stolen gondola and their Grandpa's favorite mosaic...before dinner?
When Ethan and Ella learn that their mother has accepted the position of travel writer for The Brookeston Times, they are not happy. Move away from Brookeston? Say good-bye to all their friends? What could be worse? Their mom and dad promise them that this will be a great experience, but that doesn't make the kids feel any better. The day before they are set to leave, their beloved Grandpa Harry stops by. As a gift, he gives Ella a pretty journal since he knows she loves to write and Ethan a gold coin that Ethan decides he will always keep in his pocket. But the morning of their departure, Ethan realizes he's lost the coin! Together, he and Ella must retrace their steps from the day before. Will they solve the mystery of the missing coin before it's time to head to the airport?
