When Father goes away two strangers one evening,the lives of Roberta,Peter and Phyllis are shattered.They and Mother have to move from their comfortable London home to go and live in a simple country cottage,where Mother writes books to make ends meet.However,they son come to love the railway that runs near their cottage,and they make a habit of waving every day to the Old Gentleman who rides on it.They befriend the porter,Perks,and through him learn railway lore and much else.They have many adventures,and when they save a train from disaster,they are helped by the Old Gentleman to solve the mystery of Father`s disappearance,and the family is happily reunited.