This episode tells the story of the construction in the early nineteenth century of the offshore lighthouse on Bell Rock, by the Scottish engineer Robert Stevenson. Bell or Inchcape Rock was a place which had claimed the lives of sailors and sank ships for hundreds of years, but which was underwater except for a couple of hours at low tide each day - causing difficulties in both constructing a design that would stand up to the terrible storms and waves that ravaged the area, and in actually constructing it during the few months of fair weather that were available each year, whilst simultaneously housing the builders who worked on it.