As a rule of thumb, there are only three roles for the first character who appears in a crime story. He or she can be the detective, who is investigating a crime, or the victim that will end up dead soon, or in the case of this story, the murderer.
Mrs Molly died on a Saturday, on her 50th birthday party. The policemen were called in and every member in this family and people attended the party were questioned. all of them were suspicous.
Starting from Peter, who was laid off because of Mrs Molly and claimed that he would kill Mrs Molly one day. Diane, Mrs Molly's little daughter also said the similar things on the birthday party. During the investigation we found out that she hated her mother because she blamed her mother for her father's death, she also hated her mother because her mother wouldn't give her money anymore. Albert needed money for her ill wife, who is the sister of Mrs Molly. Roger, Mrs Molly's son lost his job and had huge bills to pay for his expensive house and cars, so he also needed her money desperately. Mr briggs was losing money and wanted the garden in Mrs Molly's big house.
Everyone has a movitation to do so. Except for Jackie, another Mrs Molly's daughter, She didn't want anything from Mrs Molly. Yet she turned out to be the real murderer. At the end of the investigation, we know that Jackie hated her mother because she wouldn't let her to be with her love, Mr Briggs.
I understand the story is meant to be short, as an entry level reading materials aims for those who just start learning English. Due to the restriction of available vocabularies and length of the story, the author has not much space to develop a more vivid and sound story. Still, I think the author did quite a good job in constructing the story in a systematic way.
In every detective novel, the author has an obligation to hide the true criminals from the reader, and while doing so, he also needs to spread some bread crumbs, just enough to trigue the curiosity of the reader to follow along the story line and investigate the crime with the investigator together. In this case, The author made everyone around Mrs Molly a suspect in this crime. Yet when you follow along the investigation, you soon realise that it is always those appeared innocent that have the ability to hurt.
Another writing technique I noticed in this novel is to make things repeat more times during a story telling. In this story, at the end of every chapter, the investigater fells hungary and wants to have a sandwich. I've saw this story telling technique in multiple fictions. Authors like to describe some trivial details of the character, such as a peculiar habit when doing certain things. As I see it, why the technique is useful is that the point of making the efforts to describe irrelevant trivialities is to serve as a buffer, to divert the reader from the plot and provoke thoughts.
I missed the most obvious clue during my first reading. It is during my second reading that I suddenly realised that this crime was planned since the very beginning of the story. Jackie asked Peter to get the tablets for her mother, because she planned to kill her mother with the tablets, and letting Peter to fetch them for her, would make him a suspect. This is not a crime of passion, under the influnce of envy and hatred. There is much more cruelty in this story.
Every story has a moral. The moral of this one: You can always make more money, but love is something really scarce in this world.