Tom, Huck, and Becky, meet the legendary demigod Hercules in ancient Greece. But things aren't all that friendly as evil king Hades tries to do what he can to stop him from completing his great 12 labors. Things get worse for the kids as they're accused by Hercules himself of attemping to sabotage his labors and become imprisoned in Hades' high-tower prison as a result. Can the kids escape in time to clear their names and warn the demigod of the evil king's true intentions?

Tom, Huck, and Becky meet the legendary Don Quixote and Sancho Panza, but the adventure is just beginning when Sancho is kidnapped and the kids have to help Don rescue him in whatever unusual way they can. As confused as Quixote is, they're definitely going to need some big help as he and Tom are imprisoned with Sancho as well.

The kids are in for a surprise when they travel to an island that's inhabited by quite unusual animals. They all have to deal with a hunter who seeks to add a few trophies to his collection. Can the kids and the animals work together to stop him?

Seeking shelter from wolves in a nearby forest, Becky, Tom, and Huck are invited into a scientist's house where his hospitality turns into his own personal science project as he demonstrates his latest invention to them. It's a miniturization machine which he successfully used on a dog. But to prove its full potential, he needs a human subject. Huck becomes his unfortunate victim and in front of the others, is shrunken down to a mere 10 centimeters (4 inches). It's up to Tom, Becky, and the dog to get Huck back to normal size. But will another one of the scientist's experiments lead to their doom?

Utilizing a hot air balloon, Huck, Becky, and Tom attempt to get back to Hannibal, Missouri. But they wind up in a valley full of warring cavemen. Huck is separated from the others and found by one group of primitives while Tom and Becky wind up meeting another. As the two groups battle, Tom and Huck make things worse by helping their respective group better battle each other by introducing more advanced weapons to them. Can Becky stop them from going too far, or will another primitive tribe get the upper hand as a result of their interference?

In Ireland, Becky meets a group of Leprechauns who have trouble hiding their prescious magic shillelagh, the source of all their power. When gypsies seek this power and kidnap Tom and Huck in the process, Becky must work with the Leprechauns to keep the shillelagh out of the wrong hands and save the boys from peril.

In an African jungle, Tom is stung by a poisonous plant and it's up to Huck and Becky to find an antidote for him. Though they find a trade ship that has the medicine, it holds a secret that may lead to doom for all three kids if they don't act in time to save Tom.

When the kids save a young maiden from sacrifice to a dragon, they get in big trouble by the Guru of New Olympus. They themselves are slated to be a meal for a moat monster, but escape with some help. They need to save the maiden again and must go on a perilous mission to do so. Will they succeed, or will their fate be set in stone?

Tom, Huck, and Becky arrive in China and save a young prince from being ambushed by Mongol bandits. They however, are captured by the rogues and Tom is forced to help them find a way into the kingdom of Petchu so the bandits can loot and conquer it. With Huck and Becky as their hostages, he has little choice but to comply. The task proves even more difficult when the people of Petchu revere him as the divine one who saved the prince from capture and is held against his will, which will lead to his friends' doom unless he finds a way to escape.

While exploring an ancient Aztec temple, Tom becomes revered as its people's sun king. But is there more to this than being treated as royalty? It's up to Huck and Becky to save him from himself as they learn the truth as to what's really going on.