The Substitution Order by Martin Clark

Kevin Moore is a brilliant attorney with a lovely wife and a great future--until he discovers cocaine. Then his life quickly circles the drain. He loses his wife and his job. And has to work at a Subway knock-off making sandwiches to survive. One day a mysterious man walks into the sandwich shop trying to convince Kevin to take part in a fraud scheme. He refuses. But soon he finds himself in a world of legal trouble, thanks to the mystery man. And no one believes him except his  young coworker at the sandwich shop.

Kevin may have lost everything but he still has a sharp legal mind. And the plan he comes up with makes for some engrossing page turning. I'm looking forward to tracking down other books by Martin Clark because he does know how to tell a good story.