An Invisible Sign begins as 10-year-old Mona Gray (Bailee Madison) watches her father (John Shea) experience a mental breakdown. From that moment on, he suffers from a pervasive by undiagnosed mental illness. Unable to understand it, she relies on two divergent coping mechanisms. Even as she retreats into the logical, highly controlled world of numbers and mathematics, she also gives herself over to extreme magical thinking. The combination makes the film into something of a math problem itself, as it shows how the father’s illness exponentially affects his daughter. 

As a child, Mona promises to give up everything that gives her pleasure, if it means her father will return to normal. She also determines to take on her own pain: a montage shows her eating soap and spraying pesticide on her ice cream to show her dedication and sacrifice. Mona’s two approaches converge as the numbers from her beloved mathematics form the secret foundation of her magical thinking. She believes that if she jumps rope a certain number of times without failing, in one instance, then good things will happen to her father.

With all of this going on inside Mona’s head, how can she have room for anyone else? This becomes the math problem when, as a young woman (played by Jessica Alba), she gets a job as an elementary school math teacher under false pretenses, claiming to have a college degree when she’s actually a dropout. She also has a hard time controlling her class and sorting out her feelings for Ben (Chris Messina), the bestubbled science teacher.

Ben’s confusion is matched by ours, as Mona’s motivations are never very clear. An Invisible Sign—which opened in a few theaters and is also available on demand—is faithfully based on Aimee Bender’s novel, An Invisible Sign of My Own, where first-person narration lays out the thought processes Mona uses to justify her actions, logical or illogical. In the movie, we mostly just see the results. A voiceover dips in and out, sometimes helpfully. More often, Mona’s actions don’t suggest her ongoing struggle with her father’s illness, but instead, her own descent into madness.

Presented not as a whole character, but as a collection of tics, the movie’s Mona compulsively knocks on wood for good luck or literally runs away during the middle of uncomfortable conversations. As she focuses on her obsessions and superstitions, it’s easy to see why her third-grade class would run wild in her presence. It’s almost appalling, the ways she’s overcome by her personal compulsions at work. When she impulse-buys an axe and stashes it in her classroom, she tells herself it resembles the number seven, making it a math-related artifact. When a parent calls her a “weirdo,” it’s hard not to agree. It’s also hard to know why Ben puts in so much work to pursue her. (Unsurprisingly, he’s the one who most often triggers her flight response.)

Absent the book’s interior monologue, director Marilyn Agrelo (who made the 2005 documentary, Mad Hot Ballroom) provides a few clues as to what Mona’s thinking. Sprays of numbers and equations add visual interest, in an A Beautiful Mind kind of way, but they offer little insight into Mona’s experience. Alba does her part to illustrate Mona’s confusion, anguish, and desperation. She even looks like someone suspended as a 10-year-old, wearing tights tucked into canvas sneakers, rompers, and pigtails.

In its occasional moments of clarity, An Invisible Sign presents a moving story about adapting to circumstances. Mona’s experiences parallel those of a student in her class, Lisa (Sophie Nyweide). The girl’s mother has cancer, which leads her to behave in ways that express and also distort her pain: her bag lunch contains nothing but known carcinogens (bologna, margarine, and artificial sweetener), as Lisa hopes to share her mother’s illness. Her strategies for coping with family illness are clearer and more moving than Mona’s, and they help shed light on the ridiculousness of Mona’s fantasies.

While Lisa complements Mona and exposes her flaws, Ben mostly tries to keep up with her—literally, he chases after her. He’s not a comfort. He can’t set her straight. The best he can do is hope to manage some of her behaviors. Their romance, like the movie, remains a problem unsolved.