We begin a new episode featuring Camilla the schoolteacher who likes sleuthing, in the middle of the night, when she hears a noise upstairs. Going back to sleep doesn't seem to be an option.

Camilla is still confused in the morning, and Renzo has her read the information sheet about the sleeping pills she is taking. Berardi, Torre, and Ferrari are at work going to a new crime scene.

Camilla is still upset about what she thinks she saw during the night and goes to see Gaetano. Renzo goes to pick up Livietta at dance and can't help conjuring up the memory of the merengue teacher he had been attracted to.

Livietta tells Camilla about the scene where Giulio used a word he shouldn't have and was scolded by Renzo. Camilla is still seeing the mouse. The coroner reconstructs the murder for Berardi.

Camilla ventures up to Doctor Mattioli's office to see if the nurse is there and to ask him about hallucinations. At the police station, Piccolo is making an effort to make Ferrari like him.

Camilla can't rest until she has reported her suspicions to Berardi, and goes down to the police station before school.

The detective's mother is not able to provide any useful information to the police. Renzo finds a small object near the front entrance of their apartment building. He also gets a postcard from New York, causing not a little stress to Camilla.

Camilla is still convinced there is a mouse in the house and Renzo humors her. At school, there is some tension, but Marchesi has some information for Camilla and her mood changes. Berardi also obtains, almost by accident, some intriguing information, that could be pertinent to the case.

Camilla can't help herself and goes to the home of Mattioli's former nurse. Gaetano leaves Camilla a text message. Note that in Italy, texting while driving is now prohibited.

Camilla, in conversation with her mother, hopes that the postcard from New York is just a misunderstanding. Renzo has a moment of truth by a dumpster. Later, he says something about Dr. Mattioli that gives Camilla an idea about her "hallucinations."

The mouse is still an issue at Camilla's house. At police headquarters, Berardi has his hands full with the mother of the murdered detective and Mattioli's wife.

After her trip to the Tiber River, Camilla goes to pick up Livietta at Giulio's house, where the two kids are dancing to Merengue. Camilla has some questions about that. Meanwhile, Berardi and Torre are busy with the coroner, identifying a corpse.

Renzo comes home late after a meeting and finds Camilla on the couch deep in thought. She lets him know she has been connecting the dots between the postcard and the merengue instructor. She goes off to bed but finds a surprise on the way.

Having read about Mattioli's death, Camilla rushes to Berardi's office, where he is checking some documents with Torre. She participates and comes across an interesting piece of information.

Berardi and his men go after Marino Monti who is at the martial arts center. It was very upsetting for Camilla to see it all so close up. She has a drink with Gaetano to calm down.