Fictionalized story of British aerospace engineers solving the problem of supersonic flight.

The Waterbury family are completely happy until mysterious men take their father away and they have to move up to Yorkshire without him. The three open-hearted children soon make many friends including their Old Gentleman whom they regularly wave to on his morning train journey. Bobbie, the eldest girl, makes contact with him to try and get help for the problems they are facing. Meanwhile the children find themselves involved in several unexpected dramas on the railway