Pubblicato in Italia con il titolo Sono un assassina? Una giovane ragazza annuncia a Poirot che potrebbe aver ucciso qualcuno e poi sparisce. E Hercule Poirot ha tutte le intenzioni di ritrovarla…

A young woman shows up at Hercule Poirot’s without an appointment. She claims that maybe she murdered someone and wanted his help, until she realized that he is old… and leaves. After the initial shock for the sudden announcement – and the insult -, Poirot is intrigued by the girl and starts investigating, with the help of his friend and mystery author Ariadne Oliver. He finds out that people have their own opinion of the young girl, better known as “third girl”, as in the third girl in a rented flat, together with two other working girls, common in 1960s London. With complex family dynamics that involve an absent father and a stepmother she hates, and a charming boyfriend she loves, but everyone else disapproves of, this mysterious girl keeps Hercule Poirot quite busy.

Third Girl is an intriguing and entertaining mystery that kept me guessing until the end.