Dennis Martin was on a camping trip near the Tennessee-North Carolina state line with his family in the summer of 1969. It was an annual Father's Day tradition – all of the men in the Martin family headed to Smoky Mountain National Park to camp and hike [source: Matheny.
Dennis and his brothers had planned a prank on the adults; they were each going to jump out on different sides of the campsite to scare them. It's a pretty typical prank that should have ended with some startled shouts and then a lot of laughter. The laughter ended quickly, though, when they realized that Dennis was missing.
Family, park rangers, and other hikers spread out to search for Dennis almost immediately, but he was nowhere to be found [source: Vistaramic Journeys. That evening, there was heavy rainfall, which is bad news when you're trying to track a missing little boy.
The search for Martin became the largest in National Park Service history. One of the people searching was Park Ranger Dwight McCarter, who had successfully tracked down hundreds of missing persons, including young children. McCarter was a seasoned tracker, and he was struck by the complete lack of any sort of tracks. Dennis seemed to have disappeared completely, leaving no trace at all. His disappearance is still a mystery.
One possible lead that searchers didn't follow was a report from another family the evening that the boy went missing. The Key family allegedly heard a scream and then saw a "bear-man" with something slung over its shoulder that looked like it could be a small child [source: Vistaramic Journeys]. We'll never know whether this was related to Martin's disappearance.