在“脑性感”受到关注的社会,“常识问题儿童们”被关在屋塔房里,要解答出10个问题才能下班,为了解题展开奋战。。Miss Mary Morstan contacts Sherlock Holmes for his help regarding her father, captain Morstan, who disappeared 10 years ago. Since his disappearance she annually receives a valuable pearl by post from an unknown person. The mystery leads Holmes and doctor Watson into an intricate plot regarding a lost treasure belonging to four convicts on the Andaman Islands。