Mystery Novel: Five Little Pigs

The book that im reading is called Five little pigs, the author is Agatha Christie. So far I've read 46 pg./ 219.  The mystery is about this girl whose about to get married, but she finds out that her father when, she was about five was poisoned, and everyone believed its was his wife/ her mother, and so the women was sent to jail instead of being hanged, unfortunately she dies a year later.  The girl, Carla, gets a letter for her 28th birthday that was kept by the people who raised, the letter is from her mother, in it her mother claims to be innocent. And, so Carla hires M.Pairot, a famous detective to find out weather her mother was truly innocent. One of the words that I didint understand was: scrutiny. Scrutiny means: critical examination. A sentence would be: the scrutiny of deciphering that note took too long.