The Hidden City in Tinker Mountain

While mini-biking to the local swimming hole for a fun filled day to celebrate of the end of the school year, middle schoolers Jeff Watson and Tony Chan stumble into an adventure that changes their lives forever. The two boys accidentally discover that teenage getaway haven Tinker Mountain is home to a secret underground city of hobbit-like elves and dwarfs, and roaming bands of flesh eating trolls. A troop of dwarfs captures the boys snooping around the outskirts of the subterranean city, and accuses them of stealing some of the city's essential life giving light and energy source– gold. While pleading their case to the subterranean dwellers, who see the boys as typical gold stealing humans and fit only for troll food, Jeff and Tony learn that a mysterious illness is striking down the city's inhabitants. They diagnose the cause of the sickness as toxic waste dumping originating, incredibly, from around their own swimming hole.
Facing permanent incarceration in the city, the boys strike a deal with the city's elfin king. Jeff, with the help of the king's beautiful teenage daughter, Princess Aerial, must return to the surface world and put a stop to the dumping that is destroying the stricken city. Tony must remain behind as a "guest" of the subterranean dwellers until Jeff succeeds - and if Jeff fails, forever.
While working to stop the dumping, Jeff learns that not all girls are silly and frivolous, as the tough troll fighting Princess earns his respect and admiration, and, a place in his heart. Likewise, the Princess learns that not all humans are avaricious gold grubbing thieves, and she develops an interest in Jeff.
Jeff and the Princess apprehend the bad guys and the city is saved. In the process, new friends are made, love buds, and the untrusting inhabitants of Tinker Mountain have their faith renewed in humankind.