Little Livia is in the backseat as her mom drives another teacher home. She listens, she opens her mouth when she shouldn't, she observes. She draws her conclusions and then bets on them with her mom.

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.

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

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.

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.

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.

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.

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.

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.

Manara is back in the saddle. Raimondi leaves for Rome after a frank conversation with Luca, and another one with Marta. Quattroni has some important information weighing on him, and goes to talk to Manara.

The election results have come out, and they're disappointing. Grazia gives Adriano all her support, and this gives him the hope he needs to push ahead with his dream.

Manara, and Raimondi meet with their chief, Casadio to discuss the case and Manara's status, but the meeting has an unexpected outcome. Meanwhile, the only real suspect is Luca's sister!

Karen continues to do her work for the Americans, spying on Olivetti and the Community Movement. Dalmasso and Mauro are seriously trying to undermine Olivetti's efforts to get elected and to bring him to his knees financially.

Tiziana is confused because she has no clue that she might be a suspect. Raimondi, who shows up with Rivera, is confused because he doesn't realize Tiziana is Luca's sister. Poor Tiziana!

The laboratory team is all excited as they come up with some great new innovations. They need more funding, however, and decide to demonstrate the results directly to the board.