While there was a certain resemblance between the two lads, chiefly in the firm yet good-humored expression of their mouths, in some respects they differed greatly in appearance. While Frank was dark, with straight, black hair and brown eyes, his brother was pink-cheeked, with fair, curly hair and blue eyes.

These were the Hardy boys, sons of Fenton Hardy, an internationally famous detective who had made a name for himself in the years he had spent on the New York police force and who was now, at the age of forty, handling his own practice. The Hardy family lived in Bayport, a city of about fifty thousand inhabitants, located on Barmet Bay, three miles in from the Atlantic, and here the Hardy boys attended high school and dreamed of the days when they, too, should be detectives like their father.