If you had asked George Dalzell, a professional psychiatric social worker, a few years ago if he thought he'd be talking with the dead, he would have said, 'no way.' Yet, when his close friend Michael, an airline purser from Germany, was killed, things started happening that permanently shifted Dalzell's "perspective on reality." As a therapist, Dalzell had counseled people who claimed to hear voices. Now, Dalzell was hearing a voice himself,...