This is the twelfth story in the series, and the Five are off to Cornwall to stay with Mr and Mrs Penruthlan at Tremannon Farm.
The farm is very close to the sea, and the Five learn how, in the old days, the stretch of coast had been popular with wreckers - evil men who deliberately caused ships to
flounder on the rocks by lighting a bright lamp on stormy nights!
The Five are constantly followed around by a strange little urchin of a boy called Yan. Yan lives with his Grandad, a shepherd, high on the surrounding hills. Yan's Grandad tells the Five he STILL sees the wreckers' light on stormy nights and shows them where it comes from. The next stormy night the Five decide to investigate and, sure enough, they see the light for themselves. They are also horrified to see Mr
Penruthlan out that night, and suspect him to be involved!
A travelling theatre group called "The Barnies" arrive at the farm to give a show to the village and the Five make friends with many of the performers - in particular Sid and Mr Binks who operate "Clopper" a pantomime horse. However, the owner of the Barnies - a man just known as "The Gov'nor" - holds a deadly secret about Clopper the horse!
The Five have a dreadful shock in store for them about Mr Penruthlan too!