This is a book which belongs to the South Wales section of the plan. The author was also an artist and her eye for physical detail comes out in many of the descriptions.
She is not specific about the location in terms of naming the nearby town which is definitely on a railway line but it doesn't seem to be either Cardiff or Swansea. I suspect somewhere near Barry. The children in the story are a family of three children with two boys, Peter and Robert, who have a younger sister called Stella.
The early preoccupation of the story is with the girl who seems left out of things whilst the boys are busy building a sailing dinghy in which she has a third share. She expects her time to be taken up with looking after a female French exchange friend whom she has never met. The two boys have been to France and met the brother of the girl due to arrive. The book takes an unexpected turn when an accident happens to the French girl before she leaves home and her brother arrives as a replacement. Stella is left without a companion as the French boy,Philippe, also seems fascinated by the soon to be finished sailing boat. Yet somehow the English girl finds herself making friends with the incomer.
The pair of them are particularly drawn to the fate of a disabled man,Sammy, who in England/Wales would be regarded as "simple". For the French boy he is "a child of God" and to be treated with respect. The figurehead of the title lies on the sand near the cottage and seems to have a particular importance in the story of disabled Sammy. Sammy's aunt, who looks after him, dies and Sammy is due to be turned out of his cottage by the owners of the local estate. Sammy's care for all the injured creatures of the coast is the centre of his life and the prospect of moving into a proper and regulated form of care appals the young people and their French guest. A mystery and a secret surrounds Sammy and figurehead. This is the riddle of the title whixh is unravelled in the nick of time.
At the same time the boys are ready to launch their boat and make the first voyages. The description that surrounds the naming ceremony of the 'Evening Star' and the sudden drama that follows is just one excellent part of the plot which works its way to a very satisfactory, if not unexpected conclusion. This is a notable book for its treatment of the launch as the tide rushes in over the muddy backwaters.