The dog: The dog, Wellington, is a symbol of innocence and vulnerability. He is also a catalyst for the events of the novel, as his death sets Christopher off on his quest to find out who killed him.
The red: The color red appears throughout the novel, often in association with danger or violence. For example, Christopher sees the red of a car crash, the red of a sunset, and the red of a woman's dress. The color red also symbolizes Christopher's own anger and frustration.
The maze: The maze is a symbol of Christopher's mind. It is a complex and confusing place, full of twists and turns. Christopher often feels like he is lost in a maze, and he struggles to find his way out.
The train: The train is a symbol of Christopher's journey. He takes a train to London to find the man who killed Wellington, and this journey represents his own personal and emotional growth.
The stars: The stars are a symbol of hope. Christopher loves to look at the stars, and they give him a sense of peace and tranquility. The stars also represent Christopher's own potential, and his ability to overcome his challenges.