Pietro Gerber is a psychologist unlike any other: his specialty is hypnosis and his patients have one thing in common: they are children. Sometimes children who are traumatized or who hide memories that they are unable to evoke. He is the best specialist in Florence and collaborates with the police in criminal cases. One day he receives a call from an Australian colleague asking for help with a patient, Hanna. The case is interesting, but also very special: Hanna is already an adult and the childhood memory of her is a murder that she does not know if she committed.