This plot could appear in many novels, and one of the common ways of writing it was that the girl and the boy were childhood sweethearts who grew up together. They had a common interest and often worked for the same goal. However, in some special circumstances, the girl might leave the boy and go far away alone. When the girl returned, she might find that the boy had changed, or she might find that the boy had changed too. The plot of walking on the train tracks can appear in all kinds of novels. The most common one is that a girl encounters danger on the train tracks and needs the help of a boy. The boy may be there for the girl when she needs help, or they may face the threat of a train or other dangerous object together. This kind of plot usually makes the reader feel the emotional connection between the girl and the boy, as well as the tacit understanding and trust between them.