The brethren - John Grisham

The perfect scam: the wrong victim.

Trumble is a minimum security federal prison, home to drug dealers, bank robbers, swindlers, embezzlers, tax evaders, and three former judges who call themselves The Brethren. They meet each day in the law library where they spend hours writing letters. They are fine-tuning a mail scam, and it's starting to really work. The money is pouring in. 

Then their little scam goes awry. It ensnares the wrong victim, a powerful man on the outside, a man with dangerous friends, and The Brethren's days of quietly marking time are over.