Julian, Dick and Ann Kirrin, and their cousin Georgina 'George' Kirrin and her dog, Timmy, spend a holiday at a coastal farm in Cornwall. There, they are hosted by the garrulous Mrs Penruthlan and her enormous husband, whose monosyllabic utterances they find incomprehensible. The children encounter a young boy named Yan, as well as a group of traveling entertainers called the Barnies. The children learn that long ago, villainous locals would shine a light on stormy nights to direct ships onto rocks, so the vessels would be smashed and their cargoes washed ashore and stolen.
