how did christopher feel about his mom and how did she died

Christopher explains that his mother died two years ago. He came home from school and no one was there to answer the door so he found the key under the flowerpot and went in to make the Airfix Sherman Tank model he was building. His father came home later and asked if Christopher had seen his mother. When he said no he left the house for 2 1/2 hours. When he came back he told Christopher that he would not be seeing his mother for a while because she had a problem with her heart and she needed to rest without anyone being there. He did not look at Christopher when he said this and Christopher liked that because usually 'people look at you when they're talking to you. I know that they're working out what I'm thinking, but I can't tell what they're thinking. It is like being in a room with a one-way mirror in a spy film.' Christopher said that he wanted to make her a get well soon card and his father said that he'd take it the next day.