The dynamic universe of The Haunting of Cassie Palmer revolves primarily around the Palmer household, where young Cassie, her determined mother, and her spirited siblings, Tom and Mary, create a vivid tapestry of familial bonds. Yet, it is Deverill, the spectral entity Cassie encounters, who injects an otherworldly twist into their intertwined lives.

Cassie, though she initially perceives herself as "spineless," embodies a fierce resolve that belies her self-assessment. When fate strands her in the eerie embrace of a shadowy cemetery, she channels her trepidation into a fiery resentment toward Tom and Mary, a catalyst that propels her to fulfill her "mission" and summon Deverill. As a thinker who fiercely guards her autonomy, she grapples with reconciling her dreams against her mother's expectations. Her tactful care not to wound her mother's feelings is tested when "Mum's" frailties come to light, especially as Mrs. Palmer attempts to obscure her own deceits. Nonetheless, compassion courses through Cassie's veins, leading her to risk her own safety to shield Deverill's ghostly child from the wrath of an "orderly, clean, respectable" eighteenth-century mob.

Madame Palmer, Cassie's widowed mother, known in her profession as a medium, envelops her children in warmth and support, striving to ensure a pleasant life for the brood still nestled under her wing. Her attempts to instill virtue into her children are hampered by her own lapses, as the weight of providing for seven children alone tempts her towards more lucrative yet less honest seances. When confronted, she stands defensive and self-righteous, yet beneath the surface, one perceives her yearning for authenticity in her psychic endeavors. Her partiality towards Cassie, tied to the family's financial strain, is rooted in the belief that Cassie, with her second sight, will find triumph as a clairvoyant. Cassie's gentle reluctance to dispel her mother's illusions, as she dreams of wielding a stethoscope rather than a crystal ball, paints a tender picture of filial love and loyalty.

The gravestone bore a simple inscription: Deverill. 1720-1762. No "Rest in Peace" marked his eternal slumber. Mary, Cassie's more introverted sibling, issues a challenge to conjure a spirit, convinced that specters remain the stuff of fancy. Her stark terror of Deverill stands in sharp contrast to Cassie's hesitant delight in the ghostly presence.

Cassie's bond with her elder brother, Tom, is one of deep affection. Sensitive and astute, Tom stands as a guardian for his youngest sister, conquering his own fears to aid her when Deverill beckons her to the cemetery. With a keen perception of his mother's struggles to accept the burgeoning independence of her children, Tom's insights become a beacon for Cassie, helping her navigate the turbulent waters of their maternal relationship.

Alcock crafts Deverill, a spectral figure resurrected after two centuries of rest, with a mystique that perpetually leaves one questioning his true nature and origins, infusing the narrative with suspense. Although there is a temptation to dismiss him as no more than a vagabond, his haunting appearances at pivotal moments dismiss coincidence. His transformation into a child during his final interaction with Cassie defies mundane explanation, rooted instead in the psychic realm. Despite the ambiguity of his origins, Deverill exudes a gentle politeness, occasionally tinged with malice—not from intent, but as echoes of the bygone eighteenth-century ethos. His sorcerous suggestions for retribution, such as afflicting foes with green boils, strike Cassie as bizarre, yet he remains innocuously benign, posing no real threat. His sincere affection for Cassie shines through in the narrative's climax, as he finally earns his "rest in peace."

Cassie's odyssey with her mother and Deverill unveils the complexity of ethical dilemmas, rarely painted in stark black and white. Discovering the past and empathizing with the choices others have made fosters a profound understanding and compassion. While the theme is timeless, its subtle portrayal captivates. Cassie's internal battle between good and evil reaches resolution only when she acknowledges the blurred lines separating them. This newfound clarity allows her to appreciate her mother's sacrifices and Deverill's torments. In embracing their perspectives, Cassie matures, her empathy flowering into a deeper comprehension of the human condition.