There are roughly ten themes in this novel. They are as stated below :-
1.The Importance Of A Family - The family bond between the characters in this novel is very strong. For example, in chapter 1, mother was always at home spending time with the children. She played with them and read stories to them. Mother also read stories which she wrote to them after tea. Moreover, the children had a wonderful father who was never angry, and was always ready to play a game with them.The children loved their father and never forgot him though they never talked much about him. Bobbie, Peter and Phyllis were always together be it at the railway line, the railway station and even when they collected gifts for Perks.
2.Hope and Optimism - The children's father was always optimistic that things would be fine.For example, when Peter showed him his broken toy steam engine, father looked at it and optimistically assured Peter that he would mend it.Bobbie had high hopes that the old gentleman would be able to help her to seek the truth about her father's innocence. The old gentleman helped Bobbie in her quest because he had hopes that her father was innocent.
3.Bravery - Bobbie, Peter and Phyllis are brave children. They risked their lives to stop a train from accident. Peter and Phyllis waved their flags by standing along the railway line while Bobbie ran on to the line waving her flags. The children aslo showed bravery when they entered the dark tunnel to look for the boy in the red shirt.Mother stayed calm and brave for the chlidren's sake while her husband was away in prison.
4.The Joys Of Childhood
5.Kindness Brings Reward
6.The Loss Of Innocence
7.Justice Shall Prevail
8.Coping With Hardship
9.Resourceful And Innovative