Ghosts are the novel’s most frequently used motif. Their presence speaks to the theme of Grief and Loss because they represent how fixated each of the Bigtree siblings, but Ava and Osceola in particular, are on their mother’s death. Hilola has only recently died when the narrative begins, and Ava recalls how terrible it had been to watch their mother succumb to cancer, especially at such a young age. She and her sister Osceola, when exploring the abandoned library boat, find a book called The Spiritist’s Telegraph, which is an instruction manual of sorts on spiritualism, the occult, and contacting the dead. The children fashion a homemade Ouija board and attempt to communicate with their mother’s spirit. When they are unsuccessful, Osceola begins to commune with the spirits of other ghosts and becomes convinced that she is engaged to be married to Louis, a long-dead teenager who had once worked aboard the ghostly dredging vessel that she and Ava happen upon.

Osceola thinks herself visited, and even possessed by ghosts, and Ava too thinks that she sees evidence of Osceola’s otherworldly, spiritual possession. The Chief and Kiwi are certain that Osceola’s ghosts are a sign of a deep melancholy over her mother’s death, and Ava’s willingness to believe her sister can also be read as a sign of grief.