After learning that the father he never knew is Poseidon, God of the Sea, Percy Jackson is transferred from boarding school to Camp Half-Blood, a summer camp for demigods, and becomes involved in a quest to prevent a war between the gods.

When Orpheus, a charming mortal musician, arrives at Mount Olympus Academy, he asks Persephone to help reunite him with his lost love, Eurydice, but trying to manipulate the rules of the underworld puts her at odds with her boyfriend, Hades.

"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!"--Information...

After learning that he is the son of a mortal woman and Poseidon, god of the sea, twelve-year-old Percy is sent to a summer camp for demigods like himself, and joins his new friends on a quest to prevent a war between the gods.

"The rumor mill of Olympus is constantly churning, but Persephone and Hades are all anyone can talk about. With the constant gossip creating intense pressure on the pair, they decide to slow down their budding romance and focus on sorting out their own issues first. But that's easier said than done. Hades struggles to find support in his personal life, with Zeus trivializing his feelings and Minthe resorting to abusive patterns in their relationship....

Having proven himself capable of caring for the mythical creatures that dwell on Olympus, eleven-year-old Demon is summoned by the great god Hades to the Underworld to tend to Cerberus, the three-headed dog Guardian of the Underworld, which has been beaten by Demon's nemesis, Heracles.