How do characters' perspectives of other characters change throughout a book?

SPOILER ALERT



The book "A Murder is Announced" by Agatha Christie is, (duh) a murder mystery in which the first murder is written up in the classified section of the local paper: "A murder is announced, and will take place on Friday, October 19th, at Little Paddocks. Friends please accept this, the only intimation." For most of the book that I have read so far, the main character is Chief Inspector Craddock. He is trying to figure out why Rudi Scherz not only put the ad in the paper, but then showed up a Little Paddocks with a gun and (seemingly) attempted to shoot Ms. Letita Blacklock before shooting himself in the head. As Craddock is the main character so far, we the readers get to read what he's thinking, and to know his impressions of other characters and how those impressions change as he learns more about the different characters. As far as Craddock goes, he really judges other people by pretty much anything.

One character of whom Craddock gets the wrong impression of is Miss Marple. At first, he believes her to be an old lady who is "completely ga-ga". In other words, dumb/crazy. However, once Miss Marple makes several intelligent suggestions and gives Craddock a theory with a motive for the attempted murder, he changes his opinion completely and thinks "She was sharp, after all." This is an example of how Chief Inspector Craddock completely misjudged Miss Marple, because she appeared to be a simple old lady and started of their conversation by being flustered at meeting the Chief Inspector. However, once Miss Marple shows that she actually is intelligent and not quite the average old lady, Craddock completely forgets his earlier opinions.

Phillipa Haymes, a young widow who stays/works at Little Paddocks and has a job at another place too, at first doesn't seem like anyone very important to Inspector Craddock. Mitzi, Ms. Blacklock's foreign chef, however, seems not only crazy but suspiciously so. When Craddock questions her about the murder, she gets defensive and mean, yelling at him that's she didn't do anything. Craddock also dislikes and mistrusts her because she's a foreigner, and speaks English with a very heavy accent and not really the best grammar. So when Mitzi tells Craddock a story about Phillipa Haymes, he at first does not believe it one bit. That is, until he questions Phillipa Haymes some more. Because he's thinking about Mitzi's story, he finds pretty much everything Phillipa has to say suspicious. When its revealed that Ms. Blacklock's will leaves quite a bit of money to Phillipa, Craddock finds her to be even more suspicious, and he believes Mitzi to not be as crazy as he originally thought. So as Phillipa Haymes became more suspicious in the Chief Inspector's mind, Mitzi goes from seeming crazy to credible.

Chief Inspector Craddock is a very intelligent man, and it seems like he's the one to solve the murder at the start of the book. However, Craddock has a flaw, and that is he really judges the other characters, sometimes quite wrongly. This flaw affects the way the reader sees the characters, because as Craddock learns new information so do we. As Craddock judges the people in the book by what they say, how they look, what others say about them, etc. his perspective of the character's changes, and so does the reader's.