Lovely, affluent Christine Bravo Penmark enjoys a seemingly perfect life. She is married to a caring and well-remunerated husband, Col. Kenneth Penmark, a distinguished Air Force officer, and they reside in a posh apartment in a respectable neighborhood, all while raising their charming eight-year-old daughter, Rhoda. However, as the Colonel departs for an assignment in Washington, DC, unsettling dynamics begin to surface within the Penmark household.
Rhoda, portrayed by Patty McCormack, appears to be a rather self-centered and avaricious young girl, much to the chagrin of their landlady, Monica Breedlove, who dotes on her with lavish gifts, not instilling any true sense of gratitude in the child. Rhoda's discontent becomes particularly evident when she loudly protests having lost a penmanship competition, insisting that she was deserving of first place and all the accolades that accompany it.
To complicate matters further, they have the adult handyman, Leroy, played by Jesse White, who, despite his age, seems mentally stunted, reminiscent of an eight-year-old, making him a rather spiteful presence in Rhoda's life. His resentment toward Monica and his unsettling interest in Christine only add to the household's tension.
One day, Rhoda departs for a school picnic, adorned in shoes retrofitted with iron plates designed to mimic the sounds of tap shoes. During her departure, Leroy takes it upon himself to douse her shoes with a garden hose, bringing swift rebuke from Monica. His bitterness towards Mrs. Breedlove, combined with the evident disdain he holds for Rhoda, sets the stage for future conflict.
At the picnic, Christine engages with Claudia Fern, the headmistress of Rhoda's school, seeking insight into how Rhoda is adapting socially. Initially, Miss Fern offers flattering remarks about Rhoda, though her enthusiasm quickly wavers, leaving Christine disconcerted by her vague responses. A troubling impression is cemented in Christine's mind when she remarks on Rhoda's unnaturally mature demeanor, which she finds somewhat unsettling.
In the afternoon, Christine hosts a meeting of her "psychiatry club," where Monica proudly recounts her encounters with renowned figures in the field, making grand claims about being a patient of Sigmund Freud – a boast that raises eyebrows among her peers. The conversation veers towards dark topics, examining the case of a recently convicted serial murderess, which deeply unsettles Christine. Distraction strikes when the radio reports the tragic drowning of Claude Daigle, a classmate of Rhoda's, while playing near forbidden areas.
Upon Rhoda’s return, she exhibits an alarming nonchalance towards Claude's death, non-committal when questioned about her feelings over the loss. Only Leroy, noting her cold demeanor, suggests she's devoid of sorrow for her dead classmate. Over time, increasingly bizarre interactions unfold. As days pass, Claudia Fern reveals alarming connections between Rhoda and Claude’s untimely demise, notably mentioning that Rhoda was his last known companion and had expressed an urge to wrest away Claude's award medal, which conveniently goes missing after the boy's death.
Christine’s sense of dread escalates when it dawns on her that Rhoda's nature may not be as innocent as she once assumed. This realization only intensifies when Mrs. Daigle, Claude’s mother, flustered and intoxicated, confronts Christine, demanding knowledge of the penmanship medal, ultimately accusing Rhoda of involvement. Dark suspicions swirl as Christine begins to ponder the ramifications of her daughter's behavior.
When Christine discovers the penmanship medal among Rhoda's belongings, she confronts her daughter, who deceitfully claims possession of the medal was innocently acquired. Conflicting emotions rise as Christine grapples with misconceptions of her past and Rhoda’s sinister childishness, fearing she has unwittingly passed on a propensity for malevolence—a theory that begins to resonate deeply with her insomnia-ridden nights and dark reflections upon her own childhood.
Meanwhile, Col. Penmark sends beautiful gifts to Rhoda, a children's tea set that she cherishes. However, as Rhoda plays with her new acquisition, the hovering presence of Leroy becomes a looming threat. Stirring dark seeds of fear within Rhoda, he unveils his suspicions surrounding Claude's death. In a clever and terrifyingly innocent fashion, Rhoda deflects, yet remains aware of the significant confrontation that awaits.
As conditions worsen, shocking discoveries unfold the realities of their lives, culminating in chilling revelations that Christine now dreads about her own lineage and her daughter’s disturbing actions. She feels compelled to reveal her heart-wrenching fears of inherited criminality, particularly the possibility that her own “bad seed” may have fallen on ultracondensed soil in the form of Rhoda.
A newfound desperate resolve leads Christine to confront the bitterness that envelops her and Rhoda’s budding darkness. The climax culminates in a shattering moment of truth that severs the bond between them, provoking tragic conclusions and irreversible consequences. Rhoda, devoid of remorse, embodies an utterly chilling innocence, while Christine finds herself on the brink of total collapse, recognizing her own culpability in sowing this malevolent legacy.
The film closes with poignant reflections on familial bonds shadowed by dark secrets, leaving audiences with a lingering sense of dread and contemplation on the nature of evil and innocence intertwined. Ultimately leading to a chilling question: Are we truly masters of our fate, or mere carriers of seeds planted by generations prior?
