In the waning days of World War I, William K. Dean was brutally murdered, his body hog-tied and dumped in a rainwater cistern on his farm in the quiet town of Jaffrey, New Hampshire. Suspicion quickly fell on Dean's wife, an invalid in the early stages of dementia. Her friends, outraged at the accusations, pointed instead to a former tenant of Dean's, whom many suspected of being a German spy. Others believed that Dean's best friend, a politically powerful banker and judge, was involved.

Deep Water is based on extensive research into the Dean murder, including thousands of pages of FBI documents, Grand Jury testimonies, newspaper accounts, private correspondence, and the archives of the Jaffrey Historical Society.