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 uses her talent as an artist and applies to be a natural history illustrator for the local eccentric Orville Tanner. She documents her time on the island by writing and drawing in her journal, which is the format of the novel itself. Orville Tanner is strange and gruff and Eliza considers turning the job down, until she meets Charlie, Orville's handsome grandson. The summer progresses and a friendship develops, while Eliza finds herself illustrating peculiar finds from the chronicles of geologic time. Guided by curiosity and an uncanny sense that something is very different about the Tanner family, Eliza begins to snoop around for information. As the romance between Eliza and Charlie grows, Eliza begins to unlock the details of a family secret.