Story line

Why? 

After the cops were called to investigate the situation of the dog stabbed by the garden fork, Christopher accidently assaulted an officer which then led to his arrest. After his arrest, the police paid no attention to the matter of the dog and realised how in society dogs are still disregarded through the law and in importance. The father showed little to no emotion when Chris recounted to him the story of events. He also prohibited Chris from investigating or "playing detective" of the situation for a reason that's not completely understood. Chris talks to a neighbor of his, whom he asks her, Mrs. Alexander, if she knows anything about the murder of Wellington. She says she has no idea but asks Chris to sit down and talk. He is a man of very few words and is where we understand his lack of social understanding. He can't comprehend people's emotions and needs a diagram that Siobahn dew for him to understand the right emotion. She goes inside to get cookies leaving Chris outside, making Chris feel nervous she is ringing the police so he runs away. This is where I better understood Chris' social problems.

Turns out this secondary character will play a large role in the events of the story. Further on in the novel, Mrs. Alexander is who we learn from why Mrs. Shear's has hatred towards the Boone family. She exposes how Judy Boone cheated with Mr. Boone and made Chris promise not to tell anyone she told him that. Chris does in fact keep this promise.

Story line of the curious incident of the dog in the night-time

The climax moment comes up when Chris finds out his mother is in fact alive, which switches the focus of Wellington's death to resolving a family issue.