Reed finds himself in a deeply unsettling situation when he stands over his infant daughter, an ice pick in hand, while his wife sleeps peacefully in the other room. Despite an overpowering impulse to harm his own child, he manages to suppress this desire. However, a chilling moment occurs when the baby looks up at him and eerily states, "You know what you have to do, right?". This prompts Reed to believe he must transfer his violent urges onto someone else, leading him to target a prostitute in a misguided attempt to protect his daughter from his malevolent intentions. He convinces his wife, Marin Ireland, that he is heading out on a business trip, but in truth, he plans to rent a hotel room, hire a sex worker, and carry out his dreadful scheme.
The evening commences with Reed checking into the hotel, where he meticulously rehearses his dark plan. He wipes away traces of himself and notes down timings after nearly succumbing to chloroform. However, his intended victim does not arrive; instead, Jackie, played by Mia Wasikowska, shows up. Jackie, armed with a variety of fetish items and a predilection for sadism, complicates Reed's dark objectives. Following a tense first interaction, she retreats to the bathroom, leaving Reed in a state of mounting anxiety. When he finally enters, he is met with a shocking scene—Jackie stabbing herself with scissors. Reed swiftly overpowers her and carries her to bed, realizing that she has likely succumbed to her earlier medication. He bandages her injuries and contemplates abandoning his murderous plot, but finds himself unable to do so when he sees Jackie emerging from the bathroom, disheveled and injured.
Determined to do the right thing, Reed decides to take Jackie to the hospital. However, a chilling whisper from her suggests she "was onto him," indicating that she might be aware of his malevolent intentions. He assures her he will wait at the hospital, but as he sits there, haunted by visions of his wife offering unsolicited advice, he grapples with the uncertainty that he may still be able to fulfill his deadly desires. Fortunately, Jackie returns, seemingly happy to see him.
After establishing a fragile trust, the pair head back to Jackie's apartment, where she offers dinner. Although Reed appears withdrawn and uninterested, their conversation becomes laden with double meanings—reflecting both their sexual tension and the underlying threat of violence. As Reed begins to hallucinate, plagued by nightmares of his oppressive mother, Jackie reveals that she has spiked his meal with drugs, resulting in him once again losing consciousness. In a fit of rage, led by jealousy upon hearing Reed call out for his wife, Jackie strikes him with a can opener.
In a dramatic turn, Reed eventually regains control, but Jackie continues to disbelieve he is capable of murder. Allowing him to tie her up under the mistaken belief that they are heading to a romantic encounter, she is surprised when Reed produces the ice pick. Just as he attempts to fulfill his sinister aim, he collapses once more. Jackie, seizing her opportunity, frees herself and discovers his notebook filled with his gruesome plans.
When Reed wakes up the following day, he is bound and gagged, while Jackie methodically pierces her skin in front of a mirror. As tension builds, she prepares to turn the ice pick against him. In a moment of dread, he cries out, prompting her hesitation. After a tense standoff, she ungags him, leading to a fraught silence between them. Reed's simple request, echoing Jackie’s earlier yearning, "Can we eat first?" hangs in the air, revealing the twisted interplay of their intentions and the chaotic path their lives have taken.
