Four Blind Mice by James Patterson
Now the Mastermind is in prison, Alex Cross is ready to leave the Washington Police Force. And, finally, Alex has met a woman, Jamilla Hughes. With Nana and the kids, he is talking about the future. Until John Sampson arrives and begs him to take on one last case - his best friend has been accused of a horrific triple murder. Three women were knifed at an Army base. His fingerprints and DNA have been found - but Sampson's friend swears he has been framed, and that Alex is his only hope...Uncovering evidence of a series of suspicious murder convictions, Alex and Sampson are determined to infiltrate the closed world of the military. But what is the army trying to hide? And do the mysterious symbols daubed on the homes of the accused mean that there are more sinister forces at work?