Back at school after a week-long absence, Jimmy is confronted by the humorless school principal, Ms. Tart, who demands he explain to the class where he has been. Egged on by his classmates, Jimmy begins to tell the tale of his and the Professor's Costa Rican adventure in search of the mysterious and legendary Chupacabra. Along the way, they meet all kinds of interesting people and experience firsthand the natural beauty and adventure of the Costa Rican landscape. Whether swimming in volcano-heated waters, whitewater rafting or swinging across the jungle canopy on ziplines, there is never a dull moment for the Professor and Jimmy. Meanwhile, unbeknownst to them, Kaitlin arrives in Costa Rica shortly afterwards, having been dispatched by Jimmy's parents to retrieve their son. Luckily for Kaitlin, a nice Costa Rican girl named Annie, who offers to help her track down Jimmy and the Professor, befriends this fish out of water. As Annie tells her new classmates, it is the beginning of a great friendship, one that has ultimately brought her back to the United States as a foreign exchange student.