J.I.M. Stewart 
Open Prison [PDF ebook] 

The Head of House at a minor public school, Robin Hayes, has to break the news that his solicitor father has been found guilty of embezzlement and sentenced to two years in an open prison. He now feels he needs to prove himself afresh, but complications arise when another junior pupil turns out to be the grandson of the judge who passed sentence on his father. Nonetheless, the boys do form a relationship. A strange intervention in Robin’s life comes with generous gifts of cash from his uncle, who is also seemingly similarly supporting his father. This, however, is only the background to a typical Stewart mystery. There occurs a double kidnapping, the father suddenly and inexplicably rejects his son, the son goes to pieces and there are sufficient sub-plots to provide enough twists and turns to grip the reader as the final twist in the tale develops.