An instant New York Times bestseller!

A "dazzling debut" (Booklist, starred review) middle grade fantasy about a girl caught between the realms of the living and the dead who gets lost in the Underworld--perfect for fans of Greenwild and Rick Riordan.

Senka lives between the realm of the Living and the realm of the Dead. As ward to Charon, the Ferryer of the Underworld, Senka assists in ferrying recently departed souls across the river and into their afterlife. Although Charon has taught her many Rules about life in the Underworld, there is much he avoids telling her. Though she doesn't understand why the Rules are so important, she listens--she must heed them in order to become an official Ferryer, just like Charon.

Then a Living girl, Poppy, enters the Underworld to plead for help in finding the ghost of her brother. Poppy's grief tugs at Senka's heart--but helping Poppy goes against the very Rules Senka is so desperate to follow. When Poppy is yanked away by the river's current, Senka leaps to save her, and she and Poppy are swept downriver, far from everything Senka has ever known.

Lost in the Underwild, Senka and Poppy encounter malevolent spirits of lore and eccentric ghosts--and not all are willing to let souls slip through their grasp. Senka knows the Living can't stay in the realm of the Dead for long, and if Poppy isn't returned home soon, she will risk becoming lost to the Underworld forever. But as Senka travels deeper into the Underwild, she discovers there are secrets her guardian has kept from her, including the mystery surrounding her own existence. As Poppy and Senka dodge angry demigods, hungry wraiths, and terrifying dragon chimera, Senka gets closer to learning the truth of her own past. Soon, Senka won't just need to save Poppy's life--she'll also need to save her own.