After Charles Waterbury (Iain Cuthbertson) is imprisoned on false charges of selling state secrets, his wife (Dinah Sheridan) must move to a small house near a railway station. The Waterbury children -- Bobbie (Jenny Agutter), Phyllis (Sally Thomsett) and Peter (Gary Warren) -- occupy themselves watching the trains, even befriending a gentleman (William Mervyn) who frequents the station. When the children discover what has happened to their father, their new friend provides key assistance.