Four schoolfriends spend a summer cruise along the Carolina coast in a small dory, exploring islands, inlets, and tidal flats. Their pleasure trip turns into a sequence of adventures involving suspicious strangers, storms and wreck, spying and daring rescues, a reclusive islander, and the uncovering of hidden caches. Action scenes alternate with quieter detectivelike investigations as the boys improvise solutions, test loyalties, and show resourcefulness in peril; the narrative follows their discoveries and mishaps until a final finding resolves earlier mysteries.