Steve and Randy Day are eight and nine respectively and their summer at Moss Lake (in the Great Lakes region) with a friend of the family proves adventurous and instructive. The arrangement comes about when Mr. Day, a small town newsman, is invited to teach a summer course away from home. The boys stay with Mr. Moss at his fishing camp. There they become suspicious of two elderly gentlemen who seem to be engaged in mysterious operations- until it's discovered that they are icthyologists with a rich store of lake and shore knowledge to impart to Steve and Randy. Summery.