There have been plenty of combat documentaries over the last 10 years, but photojournalist Danfung Dennis’ “Hell and Back Again” adopts an original conceit. Dennis follows Marine Sgt. Nathan Harris, a gruff 25-year-old who was stationed in Afghanistan, during two seminal moments in his life. During an assault on a Taliban stronghold, Harris received a bullet wound in his rear that prematurely sent him home. Back in North Carolina with his wife, temporarily unable to walk and unsure of his military future, Harris drifts through his mundane life dealing with echoes of the past. Rather than letting his subject attempt to explain the trauma, Dennis shows it, repeatedly cutting between the two periods. The events speak for themselves.