Father is in trouble, and Roberta, Peter, and Phyllis have to leave their home in London and go into hiding in the countryside. Each day, the children run down to the nearby railway station, where they say good morning to the Station Master and hello to Perks the Porter and wave at the passing London train, sending their love to Father. Little do they know that the stranger on board the 9:15 a.m. train might be able to help track him down.