Katie, played by Nicky Whelan, is in a dire situation, grappling with a crying baby while engaged in a violent altercation with a man she seems to call her husband. In a moment of desperation, she stabs him with a kitchen knife, ending his life. Fast forward four years, and we meet a seemingly blissful family consisting of Angela, portrayed by Gina Gershon, her husband Brian, played by Nicolas Cage, and their adorable four-year-old daughter, Cora. Brian juggles his demanding role as a doctor while Angela takes a temporary leave to raise Cora.

Their life takes a twist when Angela’s friend Linda, played by Natalie Eva Marie, invites Angela to a Mommy and Me gym, where she introduces her to Katie, who has now returned with her natural blonde hair. It doesn’t take long for Katie’s daughter, Maddie, to bond with Cora. During their interactions, Katie reveals that she has escaped from an abusive relationship, but the specifics remain vague. Adding to the tension, Brian’s mother, Donna, played by Faye Dunaway, instantly disapproves of Katie, sensing something amiss in her background.

As Angela confides in Katie about her struggles with fertility and her reliance on an egg donor for Cora, she faces the devastating news of a miscarriage. Struggling to cope, Angela offers Katie and Maddie the opportunity to move into the guest house as a part-time nanny, hoping it will aid her recovery. One evening, Brian catches sight of Katie swimming naked in the pool, leaving him uncomfortable and confused. In an effort to regain a sense of purpose, Angela decides to return to her medical work, trusting Katie with Cora during her absence.

However, Katie’s behavior begins to raise eyebrows as she explores Angela and Brian’s personal belongings, showcasing an unsettling envy of their family life. The situation escalates hilariously when Angela discovers Katie engaged in an intimate moment in the guest house with someone she initially misidentifies, revealing a deeper relationship with Linda.

As the plot thickens, Katie learns from Linda about Angela’s plan to select her as a surrogate for their next child, stirring jealousy since Angela intends to use the last embryo from the same donor who helped conceive Cora. In a shocking twist, Katie confesses to Linda that she is the egg donor, and adds a horrifying revelation: she abducted Maddie from her birth mother in Maine because she felt the mother was unfit. In a chilling act, Katie drowns Linda in a lake, securing her own secret.

Months pass, and Katie deceives Angela and Brian, positioning herself to carry their baby while unbeknownst to them, she is also nurturing her own child. As Brian’s mother voices her concerns regarding the decision to involve Katie, Angela remains convinced that Katie is simply a surrogate, promising a significant payment without expecting anything in return. This sottisfies her questions; however, their initial bliss begins to unravel, with mutual distrust creeping in.

Angela’s worries escalate as Katie behaves more erratically. The tension between Angela and Brian rises as they decide to hire a full-time nanny despite Katie’s aggressive protests. With the family dynamic deteriorating and Angela suspecting Katie might have ill intentions, chaos ensues. Katie pretends to experience labor pains to gain sympathy and manipulate the situation, culminating in a shocking confrontation with Angela.

When Angela investigates, she realizes Katie’s delusions run deeper—a DNA test confirms their suspicions. In a desperate act of self-harm, Katie attempts to frame Angela and is rushed to the hospital for an emergency C-section. The outcome is a healthy baby boy named Gabriel, but the revelations continue to unfold, exposing Katie’s sinister past and her ruthless desire to claim Maddie as her own.

Ultimately, Katie’s actions lead to her imprisonment, while Angela, Brian, Maddie, Cora, and baby Gabriel find solace together, reclaiming their happy family life amidst the chaos of betrayal and deception. In this gripping tale of motherhood, identity, and the unforeseen consequences of trust, the line between love and obsession is testified, revealing the lengths one will go to for family—no matter the cost.