The young woman Petra (Jacqueline Lustig), on the run from police after supposedly committing a crime, takes Don Matteo hostage. While the police and Don Matteo's 'family' attempt to free him, our protagonist cooks up a plan: In order to escape and to uncover the truth, he tries to become an accomplice to his kidnapper.
The stables of an equestrian center catch fire. Suspicion falls on the old horse groom first, who has a motive to harm his employer. The employer, owner of the stables, might have a motive too - to collect insurance money. With Don Matteo's help and the aid of little boy Simone, the police uncovers the truth.