The Extortioners — John Creasey

Professor Clayton leads a double life. He is happily married, but there is another woman and also a teenage son who learns that the person he calls ‘uncle' is actually his father. Now, Clayton is being blackmailed, but is determined not to give in and approaches Inspector Roger West of Scotland Yard for help. It is important that those behind the threat do not succeed. West has to battle a vicious motorcycle gang and at the same time dodge danger to himself and protect others as he fights to prevent the truth being revealed.