Frank and Joe Hardy, sixteen and fifteen years old respectively, were the sons of Fenton Hardy, an internationally famous private detective, living in Bayport, on the Atlantic Coast. Although still in high school, both boys had inherited many of their father's deductive tendencies and his ability in his chosen profession and it was their ambition to some day become detectives themselves.
Their father had made an enviable name for himself. For many years he was with the New York Police Department, but had resigned to accept cases on his own account. He was known as one of the most astute detectives in the country and had solved many mysteries that had baffled city police and detective forces.
In the first volume of this series, "The Hardy Boys: The Tower Treasure," Frank and Joe Hardy solved their first mystery, tracing down a mysterious theft of jewels and bonds from a mansion on the outskirts of Bayport after their father had been called in on the case and had been forced to admit himself checkmated. The boys had received a substantial reward for their efforts and had convinced their parents that they had marked abilities in the work they desired to follow.
The second volume, "The Hardy Boys: The House on the Cliff," recounted the adventures of the boys in running down a criminal gang operating in Barmet Bay, and in the third volume, "The Hardy Boys: The Secret of the Old Mill," they aided their father materially in rounding up another gang.
The volume just previous to the present volume, "The Hardy Boys: The Missing Chums," told how they sought their chums, Chet Morton and Biff Hooper, who had been kidnapped by a gang of crooks and taken to a sinister island off the coast.
As the boys waited in the shelter of the rocks they talked of some of the adventures they had undergone.
"This is the first bit of excitement we've had since we left Blacksnake Island," declared Chet. "I thought we were never going to have any adventures again."
"This isn't much of an adventure," Frank said, smiling, "but perhaps it's better than nothing. Although I must say it's a mighty cold and uncomfortable one," he added. "I wonder if we'll ever have any adventures like the ones we've gone through already."
"I think you've had your fill," grumbled Jerry Gilroy. "You've had more excitement than any other two fellows in Bayport."
"I suppose we have. Like the time the smugglers caught dad and kept him in the cave in the cliff and then caught us when we went to rescue him."