Amberground is locked in darkness. A man-made star casts only a dim light over the land. The pitch-black wilderness is infested with Gaichuu--colossal insects with metal exoskeletons. The Gaichuu make travel between the cities of Amberground extremely dangerous. But thankfully the Letter Bees, a brave corps of messengers, risk their lives in order to keep the hearts of Amberground connected.

As the ferocious Gaichuu Cabernet closes in on the capital of Amberground, the Letter Bees form an army to stop it. Lag is paired off with a novice Bee who informs him that he's become a legend in the Beehive. But Lag's reputation as the "Child of Light" won't do him much good against the terrifying power of Cabernet...or the dark secret he's discovered about his hero, Gauche Suede.