The year is 1927, and the Merril children are once again in school - but one that is unlike any other. For ten months out of the year their school, set up in a Northern Ontario railway care that also serves as their home, is on the move. Thirteen-year-old Jenny Merrill loves life on the tracks, but she has a secret wish. She has fallen in love with a violin on page 244 of the Eaton's catalogue. But how will she get the money to pay for it?