The Hardy Boys are on the case in the second installment of the thrilling amateur detective series. A pharmaceutical corporation has recruited Frank and Joe Hardy's father to find missing drug shipments. The brothers join their detective father in the surveillance of an old mansion on the cliffs overlooking Barmet Bay, which is suspected of being a haven for drug smuggling. When their father vanishes, the boys must search the caves beneath the house and confront the smugglers. A gripping tale filled with mystery, adventure, and excitement!