the curious incident of the dog in the night-time 3

I saw a huge change in Christopher's father by the end of the book. When Christopher carried on with his Wellington investigation, the father and Christopher got into a fight and shortly after that Christopher found the letters that his father had been keeping from him. The father was almost in shock when he found the letters and he was extremely worried when he ran away to go find his mother, who was in fact alive. By the end, the father buys Christopher a dog and asks him to trust him again and he said that he'd do whatever it takes for him to earn his trust back.