Tad Stones (voiced in English by Kerry Shale) is a bricklayer from Spain who lives in Chicago, working on the construction of the city’s subway. Ever since he was five years old, he has dreamed of being a professional archaeologist. After being fired from his job as a bricklayer for daydreaming and for his dog urinating on the construction foreman, Tad visits his friend Professor Humbert (voiced by Mac McDonald), asking for the professor’s help in investigating an apparently vintage bottle of Coca-Cola Tad found on the construction site. The professor receives a letter from his friend Professor Lavrof summoning him to Peru to re-unite his half of a stone “key” that will unlock the legendary Incan city of Paititi. Arriving at the airport, Professor Humbert suffers an accident after taking the wrong pills and is taken to the hospital. Meanwhile, a member of the nefarious firm Odysseus Inc. is spying on them and sends the photo to the other members who are in the Sechura Desert.
Tad takes the professor’s place and, along with his dog Jeff, travels from Chicago to Cusco, Peru. in the Cusco airport Tad meets Freddy (voiced by Cheech Marin), a local hustler. Tad is kidnapped by men from Odysseus, who threaten him to give them the stone key, but Tad is saved by Freddy and Sara (voiced by Ariel Winter), Professor Lavrov’s daughter. After joining the two halves of the key, the group travels to Machu Picchu to meet up with Lavrov (also voiced by McDonald). Odysseus Inc., led by the evil Kopponen, (also voiced by Kerry Shale) again tries to steal the key, but Sara and Tad escape their clutches.