On a snowy February day in 2011, 62-year-old Cindy Sweet receives a Facebook message from a dead man-Warrant Officer Ryan Quinlan who supposedly died in Vietnam forty years earlier. He'd been Cindy's fianc before an RPG took out his "dust-off" chopper, killing all aboard. Cindy, a young combat nurse at the 24th Evacuation Hospital at Long Binh, had been devastated by her loss, but with no other choice, had served out her year in Vietnam-and even...