Phone sex operator Brooke (Jillian Janson) gets a breather on the line, but this one gets to her: "Listen, you sick fuck, I'm not into this horror movie intimidation bullshit, so either talk now or I'm going to hang up." Click. When the phone rings again, a female voice says, "Hello, Brooke. I know you're there. You don’t remember me?" The caller demands the standard greeting and tells Brooke about her recurring dream: Masturbating in her office while somebody watches—and then she turns the tables: "What about you, Brooke? What scares you? I've been watching you...."

When her office door opens, Brooke, shaken, takes cover under her desk but the "intruder" is her cop buddy Hunter (Xander Corvus). He offers to trace the number but she says, "It's nothing." She tells Hunter of her phone sex calls from his partner Bruce and his fantasies, leading to Brooke and Hunter having a set-to of their own—as the camera catches the phone still off the hook and the mystery woman listening. 

When Brooke confides in colleague Zoe (Gia Paige) that she's getting freaked out by what the Caller knows about her, the phone rings. Zoe takes the incoming call and offers to meet the caller. "I've always wanted to meet a woman who calls a phone sex line." The caller (Sarah Vandella) appears at Zoe's home, which Zoe takes in stride, and the caller hands Zoe a wad of bills "for your services." She tells Zoe to strip and masturbate, then strips and joins her on the bed, eventually leaving an exhausted Zoe blissfully asleep. Zoe wakes to find a portentous message lipsticked on her bathroom mirror: "I'm watching you."

Panicked, Zoe calls Hunter for help, and he and cop partner Bruce (Scott Nails) come to investigate. They find a picture of Brooke with a red X over her face, and Bruce heads over to Brooke's place to protect her, leaving Hunter with Zoe as the caller joins Bruce in his car, posing as another phone sex operator. Bruce has his doubts, but the caller is convincing, and besides, Brooke needs to be protected. The suspense builds as they go to Brooke's place and the caller stalks Brooke at close range. 

Director/cinematographer Francois Clousot delivers brilliant images—with night lighting, sound design, and too-close or off-center framing to build suspense—in service of a clever script. Longish sex scenes and extended chapter intros and outros betray the web origins of the material.