A man grapples with the eerie legacy of his deceased father after being released from a mental institution. Upon his return, Tom Walker (Topher Grace) inherits an imposing mansion from his wealthy father, a former senator who took his own life. As Tom faces a thirty-day house arrest, he must check in daily via video phone, or risk being sent back to the institution. His parole officer, Brody (Patricia Clarkson), harbors suspicions about Tom, hinting at a violent past involving Tom and his older brother, Alex.
The mansion soon becomes a source of psychological torment for Tom, who experiences vivid hallucinations of his late father and his father's pet dog. As unsettling noises echo through the halls and mysterious calls come from an unknown number, Tom begins to question whether the house is haunted or if he is slipping back into madness. One day, he has a vision of a girl drowning in his indoor pool, later discovering a jar containing a severed tongue—an eerie finding he initially dismisses as another hallucination.
In the midst of this turmoil, Tom finds a measure of comfort in Lynn (Teresa Navarro), a grocery delivery worker who shows a keen interest in him. However, their budding relationship takes an unexpected turn when Brody arrives for a check-up. A misunderstanding leads to a kiss that Tom does not reciprocate, resulting in Brody's aggressive outburst, eventually leaving him even more isolated.
The situation escalates when Tom discovers that Alex has escaped from prison and is now in the mansion, driven by a desperate hunt for hidden money left by their father. Tom's reality blurs further as he battles to discern what is real, even believing that Alex might be another figment of his imagination. School memories haunt Tom, revealing the traumatic past where a prank turned horrific led to irreversible consequences.
As the tension mounts, Brody arrives again with promised medication, while Tom and Alex watch a recorded message from their father apologizing for his neglect. A confrontation between the brothers leads to Alex leaving abruptly, but further chaos ensues when Lynn's visit is marred by violence. After a violent clash, Tom and Lynn must fight for their lives against Alex, who has taken her hostage.
In a desperate bid to save Lynn, Tom confronts the horrors hidden within the mansion, uncovering a secret bunker that holds the remnants of his family’s dark history. When he discovers that his mother was imprisoned there by his father, he is torn between loyalty and the need to break free from the past. Tom musters the courage to rescue his mother, only to face Alex once again.
As the story reaches a climax, Tom and Lynn find themselves in a race against time to escape the watery chaos engulfing the house, while Alex's intentions become increasingly lethal. In a harrowing conclusion, Tom confronts his family's dark legacy, culminating in a final showdown that will forever change their lives. As they step out into the light, Tom claims ownership over the mansion, saying, > "It is now," signaling his determination to reclaim his life.
