The film is about an insect-collecting man who is trying to find relaxation in the sand dunes far away from Tokyo. He misses his last bus back, but some villagers tell him that he can stay in a house that is down in a pit basically. He agrees, and climbs down the rope ladder into the pit. A widow lives there by herself, but she is young. During the night, the man notices that she is shoveling the sand. When he tries to leave in the morning, the rope ladder is gone. He is trapped. The woman tells him that they have to shovel the sand (it is pulled up by ropes to the villagers at night, who sell it, under the table, to be used in construction, since it's too salty, technically, for construction). If they don't, their house will become buried in sand. And the house next to theirs will then be in danger. He tries refusing to work, and tries to escape, but he is always returned to the pit. He becomes the widow's lover, but he still wants to leave, badly.
