Two quests down, one to go! Then, hopefully, King Eurystheus will finally forgive Hercules and not declare war on Mount Olympus. Zeus nd Hercules have acquired the Amazon warrior queen's golden belt and the Hydra's scale. All that's left is to bring Cerberus, the three-headed guardian of the Underworld--gulp!--to King Eurystheus. Hopefully, Athena can get Hades to loan them Cerberus until the quest is completed. But when the trio arrives at the Underworld, they find a zombified Hades. Then the mysterious Melinoe steps out from the shadows with her skeleton ghost army known as Nightmares--double gulp! How do Zeus, Athena, and Hercules even fight an army of ghostly skeletons?

"Zeus and his fellow gods-in-training face a new challenge in the underworld when they attempt to capture Cerberus,the three-headed guardian and cherished pet of Zeus's brother Hades. But they find themselves up against even more than they anticipated when they have to face off against Melinoe and her skeletal minions"--

When ten-year-old Zeus is kidnapped, he discovers he can defend himself with a magical thunderbolt.

Zeus and his friends are back for another adventure in this latest Heroes in Training chapter book! Since defeating the Titans, Zeus and his fellow Olympians have taken over Mount Olympus. Things are nearly back to normal…until a stranger named Hercules shows up, asking for help. He’s on the run from Eurythseus, King of Argon, who is after Hercules for egging his temple. Before Zeus can help, Eurythseus himself appears. It turns out that Hercules has also been bragging that he is the ruler of Olympus, and Eurythseus intends to declare war on the Olympians’ new home. Zeus’s friends come up with an idea—maybe Hercules could make up for egging Eurythseus’s temple. The Oracle Pythia reveals that in order to do this, Hercules must get a scale from a huge, nine-headed serpent—the Hydra. Will this be enough to please Eurythseus? Or is another battle on the horizon for the Olympians?

The Heroes in Training are entering the Underworld—if Hades can conquer his canine fears, that is. The Underworld usually isn’t really meant to be a fun place—but tell that to Hades! He loves the dark and the stinky smell of sulfur. However, there is one thing that Hades is not a fan of: dogs. And when Zeus and his fellow Olympians encounter Cerberus—a snarling, three-headed dog—Hades must conquer his fears and tame the hound so everyone can continue into the Underworld and deposit their Titan prisoner, Oceanus, back where he belongs! But with magical water that causes forgetfulness, hot beds of lava, and another epic battle with two more Titans standing in their way, will Zeus and his heroes make it out of the Underworld with everyone intact?

The Olympians must face the fierce giant Typhon in order to find magic seeds that will help grow the earth after the terrible drought brought upon the land by Hyperion.

Zeus and his friends try to free Briar, Kottos, and Gyes from Tartarus so they can finally beat Cronus once and for all in this Heroes in Training adventure. The fourteen Olympians and Ron are headed toward Olympus. Ron is telling them the rumors that the Titans have all escaped Tartarus and are gearing up with Cronus for a final battle with the Olympians. When they reach the sea, Oceanus attacks them by surprise. They are almost washed away by a tidal wave when mysterious woman appears and saves them. It is Gaia, the wife of Uranus—and grandmother to Zeus and most of the Olympians. Gaia is on the side of the Olympians, partly because she believes that they will be better for the planet than Cronus, but also because she is angry with her son. He has imprisoned his three brothers: Briar, Kottos, and Gyes. She says if the Olympians free them from Tartarus, they will help the Olympians defeat Cronus. But can the three brothers be trusted? And can the Olympians defeat Cronus once and for all?

After a sea battle between the Olympians and the Titans, the Olympians find themselves shipwrecked on an island, and when Uranus' stars falls into the ocean, a dangerous wave of bubbles heads towards the island.

With a clue from the oracle Pythia, the Olympians head to the Land of Grapes where they encounter Dionysus, who they suspect is also an Olympian with great powers, but he could turn out to be a hindrance in their attempt to dethrone King Cronus.

When the goddess Artemis goes missing, she is believed to have been kidnapped. And now it's up to Percy and his friends to find out what happened. Who is powerful enough to kidnap a goddess?