Luca goes to see Ginevra about the autopsy, but he confides in her, too. Toscani is having trouble telling Luca the results of his investigation into the passengers of the bus.

Arianna prepares the ingredients for the panzanella and stresses that this recipe is easily adaptable to personal tastes. You can't really go wrong. It's also a great recipe for anyone to make while vacationing in Italy, since it's so simple.

Karen sends a clear message to Adriano and they meet. She has something important to tell him.

Martino makes an important decision, but gets stopped in his tracks. He's going to have to change his plans.

The protest at school continues, and there is tension among the teachers and the principal. At home, Renzo has a first encounter with the housekeeper. He finds her a bit odd.

Lorenzo is seriously upset with his mother. He wants to be left alone, but Eva has a hard time with that. On a different front, Eva goes to see Augusto for advice and help regarding the mechanic.

The contents of the blue backpack point to a possible motive. Luca talks to his sister again, but she is still visibly upset, which is understandable. Marta finally talks to Luca about what has been weighing on her for a while.

We have a look at two important medieval manuscripts in the State Archives. They are the original Constitution of the Republic of Siena. Alberto Angela gives us some fascinating facts concerning it that reaffirm how wise the rulers of that republic were.

Christmas dinner is interrupted by a phone call from the plant, where engineers are working. Karen listens in. She then has an ominous meeting with the Americans.

Peppino brings Martino some magazines singing his praises. But the two friends don't agree on what should happen next, and things get unpleasant.

There's a problem at school, and of course, our Prof (short for professore [professor, teacher], the affectionate, abbreviated term students use in addressing a teacher) has to investigate.

Lorenzo is giving his mom the silent treatment and this is torture for Eva, who recognizes she was wrong and wants to talk about it. Eva gets some new information from Franco who is taking a look at Dante's motorcycle.

During questioning, the passengers seem to agree about one person getting back on the bus during the rest stop: Luca's sister. Buttafuoco and Barbagallo finish up checking the luggage, but they come across an extra bag.

Arianna, born and raised in Tuscany, will make panzanella, one of her favorite dishes. The main ingredient is quite humble: stale bread!

At the Olivetti home, it's Christmastime, and there's an air of celebration among the members of the extended family. Karen, who is listening in, is engulfed by feelings of nostalgia for her mother.