After meeting a water naiad named Minthe in the gloomy Underworld, Persephone feels especially grateful for the happy life she leads. In contrast, Minthe has to guard the stinky river Cocytus with no friends around her. When the students of Mount Olympus Academy are challenged to a geo-dashing competition on Earth, Persephone wants to win! But it turns out Minthe is definitely a little green with envy over Persephone and her friends. And when the challenge takes the team to the Underworld, Minthe shows her true colors and causes big trouble for the team! Can Persephone figure out how to save her friends and how to become a friend to Minthe?

Minthe -- Late! -- The competition -- Teammates -- Disappointment -- The first clue -- Pirithous problems -- The white blackbird -- Clue two -- The last two clues -- The chair of forgestfulness -- To the rescue! -- Mealtime at Moa.