In 1992, a young girl named Rebecca Summers ventures out to her family pool one night, driven by a simple task: retrieve a toy boat that your terminally ill brother, Tommy, cherishes. As she struggles to reach the boat, something unseen tugs at her, pulling her beneath the surface and leaving a chilling hush behind the splashes of water. The event foreshadows a deeper, darker pull that will echo through the years.
In the present day, the Waller family—Ray, Eve, and their children Izzy and Elliot—search for a new home after Ray’s baseball career is cut short by multiple sclerosis. They settle on a house with a spacious backyard pool, drawn in by the promise that the water might aid Ray’s condition. The house seems almost too perfect: when Ray clears debris from the pool, maintenance workers reveal that the pool is almost self-sustaining, drawing its water from a hidden underground spring. This discovery brings a strange sense of reassurance, and Ray begins to spend more time in the water as part of his therapy.
However, as Ray’s time in the pool increases, the mood at home shifts. Ray’s MS appears to go into remission, but the change in him feels unsettling, not simply therapeutic. Eve notices subtle, growing alterations in her husband—precautions that feel less like recovery and more like possession by an unseen force. Izzy and Elliot also endure strange, violent incidents: both are attacked by something lurking in the pool, and the family cat vanishes without a trace. A festive pool party exposes the tension further when their realtor, Kay, drops a troubling old note: the previous owners’ daughter drowned in this very pool, and Ray’s health crisis is strangely intertwined with those past events. The unsettling pattern hints at more than bad luck or coincidence.
To uncover the truth, Eve digs into the neighborhood’s history and seeks out Lucy, Rebecca Summers’ mother. Lucy reveals a shocking secret: the water that now sustains the pool was once part of an ancient healing spring guarded by a malevolent, fairy-like entity. The spring’s gifts come at a price—someone must be sacrificed to the guardian to unlock its healing powers. Lucy explains that she sacrificed Rebecca to save her son, Tommy, and that the pool’s restorative properties are inextricably bound to a dark bargain. The revelation hits Eve with a cold realization: Ray’s apparent healing may come at the cost of one of their own children, trapped and at risk because of the pool’s guardian.
When Eve returns home, she finds Ray under the entity’s control, a force overtly manipulating him to threaten Elliot and endanger Izzy. The evil presence asserts itself through the water, making it feel alive and malevolent. Desperate to save her children, Eve confronts the nightmare with courage, while Izzy faces the guardian head-on. Izzy uses a baseball bat to physically challenge the entity’s control, trying to sever the link between her father and the spring. Meanwhile, Eve frees a frightened Elliot from the pool’s grip, guided by the lingering presence of Rebecca Summers’ spirit, whose appearance becomes a beacon of hope in the chaotic struggle.
Back in the yard, the family’s combined struggle—Izzy’s fierce stand, Elliot’s fragile condition, and Ray’s diminishing control—begins to turn the tide. Ray, driven by love and the will to protect his children, makes a final, devastating choice. He sacrifices himself to the entity, an act that breaks the hold and causes the guardian to vanish. The pool’s threat is neutralized, but the cost is grave and deeply personal.
In the aftermath, Eve, Izzy, and Elliot decide to stay in the house—but with a radical change: the pool will be filled in to prevent any future harm from the guardian’s reach. The family clamps down on the danger of the ancient spring, choosing safety and sanity over the eerie gifts of the water. The story closes on a note of quiet resolve: the memory of Rebecca Summers’ tragedy remains a stark reminder of the price of healing, and a family vow to protect one another from any lingering shadows cast by the pool’s dark past.
