The two half-orphans Reni and Rolf are 13 and 10 years old and they live with their grandmother in Berlin. Their father has died during the war, their mother works at a Baltic Sea port. Here she meets a captain who wants to marry her. When their mother tells them about the planned wedding, Reni and Rolf are reluctant to meet the captain.

On a barren and stormy island, fishing families eke out a meager existence on what they can catch during summer, and what washes ashore during winter. But little has been washing ashore of late, and their situation worsens. Elders recall how twenty years ago, when the lighthouse keeper’s beacon went dark, a cargo ship broke apart on the cliffs. It proved a bountiful accident for the fishermen. Today people on the island view the conscientious lighthouse keepers with evil hungry eyes...