Diana is a 12-year-old girl who lives secretly on the overgrown grounds of Oak Hill Manor. Bound by a strict set of personal rules, she survives in the woods alongside her brother, actively avoiding the view of any adults who come to the property. While she is normally a careful rule-follower, the arrival of a girl her own age sparks a deep longing for companionship that tests her boundaries.

Georgie is Diana’s eight-year-old brother and her constant companion on the Oak Hill Manor estate. He relies entirely on his sister for entertainment and security, firmly believing that they do not need anyone else in their lives. He enforces their personal rules strictly and views any new arrivals on the property as an immediate threat to their isolated existence.

Lissa Morrison is the 12-year-old daughter of the estate's new caretaker. Following the death of her mother, she endures a nomadic, homeschooled life with her father, leaving her feeling severely isolated. She frequently writes in her diary to cope with her lack of peers and holds onto a cherished teddy bear that provides comfort during their constant moves.

Miss Lilian Willis is the deceased former owner of Oak Hill Manor whose presence still casts a dark shadow over the estate. During her life, she maintained a cruel and haughty demeanor, alienating those who worked for her. Her imposing, empty mansion serves as a constant reminder of the fear she inspired in the local residents.

Mr. Morrison is an aspiring writer who accepts short-term jobs as a caretaker to support his small family. He prefers a quiet, secluded environment and actively keeps his daughter out of public schools, believing traditional education stifles imagination. He completely dismisses the local rumors about the old Willis place, maintaining a strictly practical worldview.

The parents of Diana and Georgie previously lived and worked on the Willis farm. They provided a warm and loving home for their children before a tragic shift in their circumstances separated the family entirely.

Lissa’s mother passed away when Lissa was five years old. Her death profoundly affected the surviving family, causing Mr. Morrison to adopt a wandering lifestyle and leaving a lasting emotional void in her daughter's life.

Macduff is the large, protective dog belonging to the Morrison family. He displays a keen sensitivity to the strange environment around the old Willis place and fiercely guards his owners from potential threats in the woods.

Nero is a black cat who wanders the grounds of the estate alongside Diana and Georgie. When the Morrisons move into the caretaker's trailer, Lissa quickly notices the cat and attempts to adopt him under the name Aladdin.