Diana is the protagonist of The Old Willis Place, the story being told from her first-person perspective. She is 12 years old and spends her days on the grounds of Oak Hill Manor with her younger brother, Georgie, and their cat Nero. It is later revealed that Diana is not a living girl, but a ghost trapped on the property where she died decades ago. Her routine comprises playing with Georgie and rereading Clematis, the only book she has.

Diana loves reading, but it has been a long time since “[she’d] had anything new to read. Or anyone to talk to besides [her] brother” (6). For years, Georgie has been the only person in her life, just as Clematis is the only book she owns. When Mr. Morrison moves in as the new caretaker of Oak Hill Manor, he brings boxes of books with him—books the siblings plan to “borrow.” More importantly, he brings a daughter who is Diana’s age, Lissa. Despite being a rule-follower, Diana becomes determined to befriend Lissa and contemplates breaking her and Georgie’s personal rules in order to do so.

However, complications arise. When Diana first breaks the rules by making herself known to Lissa, the latter thinks the former is a “horrible creature” (50), describing the girl as a “monster” (49) with dirty clothing, tangled hair, and sharp nails in her diary.