One Way Out - Allan A. Goldstein

Harry Woltz is a homicide cop with a gambling problem; a problem that leaves him owing a great deal of money to the Russell brothers. To clear the debt they ask him to train John Farrow to murder his wife, Evans, without leaving the usual clues or making the usual mistakes. However when Harry's ex-partner is put on the case, she begins to get closer than Harry had thought before the case takes some unexpected twists.