May, portrayed by Angela Bettis, is an awkward and isolated young woman struggling with the heavy burdens of a troubled childhood stemming from her "lazy eye." This condition made her feel different, and as a child, her mother took her to an eye doctor who suggested wearing an eye patch. Instead of helping, this only drew unwanted attention from her peers, as one child famously asked if she was a pirate on her very first day of school. As May grew, she found herself with limited social interactions, leaning on her only companion, a glass-encased doll named Suzy, a gift from her mother with the moral, "If you can't find a friend, make one."
As an adult, May works at a veterinary hospital in a lower-class neighborhood in Los Angeles, where she assists in various surgeries. To correct her lazy eye, her optometrist first provides her with regular eyeglasses and later a specialized contact lens. In an effort to connect with the world around her, she becomes infatuated with Adam, played by Jeremy Sisto, a local mechanic. Her fascination leads her to synchronize her schedule with his so she can watch him discreetly. When she finally musters the courage to approach him, she admits her quirks, to which he responds, "That's okay. I like weird." Their relationship begins to blossom, and Adam becomes a gateway for May into a new world of emotions and experiences, even teaching her to smoke.
Meanwhile, May's co-worker, Polly, portrayed by Anna Faris, shows a burgeoning interest in her, while also teasing her about being odd. At one particular moment of vulnerability, May compliments Polly's neck, which leads Polly to gift her a cat named Loopy due to her landlord’s stringent rules against pets. May's infatuation with Adam takes a darker turn when he introduces her to his university film, a black-and-white silent piece about lovers engaging in cannibalistic acts. This revelation leads to an intense moment where she gets carried away during a passionate kiss and inadvertently bites Adam, drawing blood, which deeply disturbs him and propels him to end their relationship.
Feeling guilty and blaming her doll Suzy for her poor choices, May becomes increasingly isolated after overhearing Adam and a friend derisively label her a lunatic. In a twist of fate, she succumbs to Polly's flirtations, diving into a romantic relationship that offers brief solace. Afterward, May seeks a job at a school for disabled children, hoping to connect with a lonely girl named Petey, whom she feels sympathetic towards.
As her relationship with Adam fades, May’s mental state deteriorates. In a moment of rage, she accidentally kills the cat Loopy, further isolating her existence. Over time, her obsession with her doll Suzy transforms into delusion, and she begins to hear Suzy speaking to her through crackles from her shattered glass case. Desperate and lonely, May visits the school for blind children and shares Suzy with them. However, chaos ensues when the doll falls, cutting both May and the children, leaving her drenched in their blood.
In a striking moment of emotional turmoil, May meets a punk named Blank, played by James Duval, who displays interest in her peculiar madness. Yet, when he finds the corpse of Loopy wrapped in plastic, he panics and calls her a freak. The encounter spirals into violence, as May, driven by her frustration and anger, stabs him.
The film reaches a climax on Halloween night, where dressed as Suzy, May adopts a normal demeanor and coldly interacts with Polly and Ambrosia before culminating in a horrific series of murders that reveal her desperate need for connection, albeit through violence.
In the end, May attempts to create her ideal friend, sewing together parts from those she has murdered, and names her creation Amy, seeing in it the possibility of companionship. After a psychological meltdown, she pierces her own eye, connecting painfully with her creation. As she leans against Amy, her mind conjures a vision of friendship and comfort, an escape from her solitary existence amidst the terror she has unleashed.
