Eliza Wolcott has been sent by her parents to live with her aunt and uncle for the summer on the small community of Orcas Island off the mainland of Washington State. What she imagines to be a fun-in-the-sun vacation quickly turns into a season of assuming responsibility as she is forced by her uncle to get a summer job. Eliza utilises her talent as an artist and accepts a job as a natural history illustrator for the local eccentric Orville Tanner. While Mr. Tanner is strange and gruff, his grandson Charlie is friendly and handsome. As the summer progresses Eliza finds herself illustrating peculiar finds from the geologic past. Guided by curiosity and an uncanny sense that something is very different about the Tanner family, Eliza begins to snoop around for information and unlocks the Tanner family secret. Eliza documents her time on the island by writing and drawing in her journal, which is the format of the novel itself.