From the novel, "The Railway Children", the one event that I find very sad is when father was arrested by two government people in the house in London. Father was accused of being a spy and mother did not tell the children about this. Bobbie found out about the news in the newspaper many months later.
One evening, the family received two unexpected guests at their home. Two gentlemen came to see father and they were having a long argument in one of the rooms. Then father went away with the two gentlemen and mother did not tell the children anything. The few weeks after, things went terribly wrong. Mother was always out and then the maids went away.
One day, mother told the children that they had to leave their house in London and move to the country and live in a little white house near a railway line. They children did not go to school because they did not have enough money. Mother wrote stories and sold them to the magazine, and then there would be cakes for tea. When it rained and the day got cold, there was no coal for them until Peter had to steal some coal from the Railway Station.
At one time, mother got very sick and needed some items listed by Dr. Forrest to be cured. Unfortunately, it was impossible to get them as they were poor. As a result, the children had to ask for help from the Old Gentleman in the train, even though mother did not agree.
The event when father was arrested is in fact the saddest part of the novel. This is because after that incident, the family had to be separated. Mother and the children were forced to move away. And to make matter worse, they had to live in a poor condition. Lucky enough, at the end of the story, father was released and reunited with his family again.