The German lightship (permanently anchored floating 'lighthouse') Borkum Riff is about to be decommissioned. For his last tour of duty, Captain Johann Freytag brings along his near-adult, estranged son Fred. The ship picks up three men stranded in a broken-down boat--who are armed. The captain tries to avoid trouble, but the crew, his son, and the trio of violent robbers on the run keep rejecting his nonviolent advice, which leads to repeated bloodshed.