Edith Nesbit 
The Railway Children [EPUB ebook] 

‘The Railway Children’ are Roberta, Peter and Phyllis, three young children who move to a house near a railway when their father is wrongly accused and falsely imprisoned for selling government secrets to the Russians. The children pass the time by watching the railcars go by and waving to the passengers riding the train. Eventually they meet Perks, the station porter and an old gentleman that may be able to help get their father out of prison.