Four Blind Mice book by James Patterson

Detective Alex Cross is on his way to resign from the Washington, D.C., Police Force when his partner shows up at his door with a case he can't refuse. One of John Sampson's oldest friends, from their days in Vietnam, has been arrested for murder. Worse yet, he is subject to the iron hand of the United States Army. The evidence against him is strong enough to send him to the gas chamber but Sampson is certain his friend has been framed.

Drawing on their years of street training and an almost telepathic mutual trust, Cross and Sampson go deep behind military lines to confront the most terrifying-and deadly-killers they have ever encountered.

On his visits home, Alex must confront another, more harrowing mystery: what's the matter with Nana Mama?