Karl Platen is the ferryman in a remote part of Germany. His job is to pull the rope and get the ferry from the pier (a few wooden boards) on his village across the swampy marshes to the pier (a few more wooden boards) on the other side. That's his job - back and forwards all day carrying whoever wants to take the ride for a small payment. A gong is sounded to alert him if someone is waiting. This place is very secluded so it's not a hive of activity. An ominous customer takes a ride with him and that's the end of Karl. Sybille Schmitz (Maria) takes his place and she has to deal with the supernatural mystery that unfolds.
Death figures prominently in this story. I don't just mean death, I mean Death the person. At the story's end I was reminded of the Greek tale of Orpheus and his journey to the Underworld in order to save Eurydice. He has to lead her out and not look back or he will lose her to Hell forever. Well, he nearly makes it but looks back at the last second. And that's that! It drew a parallel for me when Sybille is leading Death through the swamp, although in reverse, ie, don't look back in order to destroy rather than to save.
I like to read the film's ending as a spiritual awakening of sorts for all concerned. There are some inconsistencies in the story but we are dealing with the paranormal here, so just let them be and enjoy the folk tale and the story's atmosphere. I watched this film and noted that Death never paid for his ride on the ferry boat and this annoyed me. It's really inconsiderate.