The Ferret, The Donkey and Snakesbelly

Derek Rafferty's brother-in-law, Dean, has been sent to prison. He is mid-forties, respectable, married for twenty-five years with three grown-up kids and never before been in trouble with the law.
As an ex-copper, Rafferty needs to find out how this has happened.
Whilst visiting his sister during Dean's absence he comes across some evidence that all is not as it has appeared. He decides to carry out his own investigation and, not wanting to rely on the traditional justice system with which he has lost faith, proceeds to act as prosecutor, jury and judge.