Seven-year-old Riley recently lost her mother and struggles to cope with her grief. Her family moves into her mother's childhood home, a grand, old house filled with memories and secrets. Riley, feeling isolated and alone, soon befriends an imaginary friend named Sam who helps her navigate her emotions and the challenges of her new environment. Sam's presence initially offers comfort, but strange occurrences in the house hint at a deeper, more unsettling reality.

Riley's older sister, Claire, begins to notice Riley’s increasingly peculiar behavior and grows concerned. Claire investigates the house's history and becomes convinced that Sam might not be as imaginary as Riley believes. As the mysterious events escalate, Claire faces the pressing need to protect her sister from an unseen force tied to their family's past. The siblings must navigate a labyrinth of secrets to uncover the truth and ensure their safety, forcing them to confront their own fears and the dark shadows lurking within their family legacy.