Mia (played with force by horror queen Alyssa Sutherland) is a pregnant woman living in a middle-American suburb, surrounded by seemingly happy families. But the guilt and grief from losing her beloved son Axel to cancer 10 years earlier still dominates her painful existence.

Group therapy with other parents who have lost children—to illness, accidents, abduction, and other tragedies—offers Mia some comfort by reminding her she is not alone in her shattered life. She forms a significant friendship with John, the father of a missing boy named Henry, whose all-consuming conviction cost him his job and relationships. As John (a powerful performance from Jonathan Rhys Meyers) becomes a source of relief for Mia’s inner turmoil whenever she sees her dead son in children on the street, their bond and her psychosis spiral into deeply disturbing territory.

As Mia moves through her isolated routine, she discovers a beautiful stray dog in need of care. Bringing him home and nursing him back to health gives her renewed purpose and a reason to keep going without Axel. Then, one day, the dog runs off and is found in the arms of Simon, a troubled boy who seems detached, and wary of Mia’s concern.

Simon and Mia connect through the emptiness left by his mother’s absence and her own fractured family. As their similarities emerge, Mia begins to imagine bringing the solemn, abused boy into her home as a second chance at life with Axel.

The disturbing scenes that follow gradually point to a grotesque presence hidden inside Mia’s eerily decorated house, forcing her to feed and nurture it with human blood. Clearly born from her deranged hallucinations and fixated on Simon in a terrifying way, Mia’s psychotic break strains her rapport with John, who only wants to help her through her trauma.

When Simon is reported missing, John’s former “detective” instincts resurface as he tries to prevent anyone from enduring the same pain he suffered after Henry vanished. Flashbacks of Mia with Axel, John with Henry, and the nightmares stalking every character in The Room Below build an overwhelming tension, opening multiple mysteries that must be unraveled before more blood is shed—and more devastation follows.

Simon’s resolve and attempts to escape grow increasingly desperate and punishing as Mia clings to her belief that he calls her Mom because he “is her Axel.” The Munchausen mother guards her secrets, unknowingly tormenting John as he frantically searches for the abducted boy. In this cat-and-mouse game of deception, the grief, anxiety, and anguish from 10 years earlier come rushing back.

While the house creature’s control over Mia functions as a deliberate metaphor, one could argue it is unnecessary; Mia appears deeply disturbed even without the crutch of feeding the demon within. The same question applies to John’s disabled wife, Mary, whose presence feels only marginally relevant in this suffocating story of loss and obsessive despair.

At the end of it all, there’s one thing learned from this frightening tale: Never underestimate the delusions of a grieving mother.