This could be called a thriller about trains. It is set in Cumbria on the Carlisle to Barrow coast line in the 1970s, when there were plenty of trains running on that line, and St Bees had a manual signal box. Stephen, aged 11, sometimes helps his uncle Dave in that signal box. They both have a great interest in railways generally, and are sometimes volunteer workers on the Ratty - (the Ravenglass to Eskdale) the preserved line that runs 15? gauge steam locomotives. Stephen lives in Whitehaven with his mother and brother, but often helps his grandmother, who does bed-and-breakfast and evening meals in her house in St Bees. A mysterious stranger books in for an indefinite stay one April. Stephen takes a instant dislike to him without knowing why. Thereafter it seems that wherever he goes, Mr Arbroax is there too, and Stephen becomes ever more uneasy throughout the spring. While cleaning Mr Arbroax's room one weekend he looks in the suitcase under the bed, which, according to its owner was heavy because it was full of books. When Stephen finds a jemmy, a crowbar and sundry other items, but no books, his suspicious become fears. In the penultimate chapter, a heroic deed is required of Stephen and he rises to the occasion very bravely and with very good effect.