The Cornish coast of England is selected as the ideal spot for vacation by five adventurous boys and girls who, with bag, baggage and bicycles, arrive at the Penruthlan Farm with the vow to leave sleuthing and mystery-solving out of their orbit of interest. But as fate would have it, their fascination with an old neighbor's tale of shipwreck leads them headlong into a modern day smuggling operation. In Grandad's day, evil looters would ships in a fatal trap by placing a guiding light among the treacherous coastal rocks- whereupon the victim vessel would be smashed to smithereens and its cargo left to these men of prey. With the children's clever deductions and investigations, they uncover the head of the dope ring in their own midst and learn how the old Wreckers' method and hideouts were utilized in his schemes. A skillfully written mystery with a strong accent on regional flavor and British personalities.