The Summer House by James Patterson

One historic lake house. Seven murder victims.Four accused Army Rangers. Two versions of the truth.Only one can survive.
Sullivan County, Georgia, belongs to Sheriff Emma Williams. But not when Army Rangers posted to the local base are implicated in a major crime. To an elite team of investigators led by Major Jeremiah Cook, the physical evidence Williams swears by presents clues to an entirely different story. The small-town sheriff has never worked a multiple homicide, and Cook knows it. Unless he can convince the locals that the recent crimes are part of a larger mystery, this outsider may never unlock the century of secrets hidden inside The Summer House.