"My family found safety in numbers," Mona Gray (Jessica Alba) explains in An Invisible Sign's opening voice-over, "with us, one plus one equaled three." Groan. Shortly thereafter her father (John Shea) is subtracted from the formula, and Mona spends the next ninety minutes trying to balance her life's equation.
After renouncing fun as a kid in hopes that her sacrifice would solve her father's illness, Mona grows into a maladjusted and unmotivated twentysomething numbers nerd. When her mother (Sonia Braga) lands Mona a job teaching math at her old school, tentative relationships with students and science teacher Ben (Chris Messina) begin to coax her from her shell. Adapting Aimee Bender's 2001 novel An Invisible Sign of My Own, screenwriters Pamela Falk and Michael Ellis and director Marilyn Agrelo add family drama to romantic comedy and inspirational teacher genre tropes, though these never amount to the sum of their parts.
Mona finds her foil in the precocious, emotionally unbridled Lisa Venus (Sophie Nyweide), a bright outcast in the third grade math class whose mother has terminal cancer. Like Mona, Lisa wants to sacrifice herself to save her ailing parent, even choosing to perform cancer in a science class acting exercise. Mona, for her part, has no idea how to act around Ben (Messina) and falls back on nervous ticks like compulsive knocking and soap-eating—ominous close-ups on her bathroom bar of soap fail to be anything other than hilarious. Also in the mix are the class's bratty rich girl Anna (Mackenzie Milone) and Mona's old math teacher neighbor (J.K. Simmons) who wears numbers corresponding to his mood around his neck and provides surprisingly lucid life lessons after being interrupted mid-coitus.
An Invisible Sign diminishes its greatest assets—the relationship between Mona and Lisa, Shea's strong performance of delusional disease—by continually visualizing the invisible, and verbalizing the already overly emoted. When Mona taps nervously—as her father rhapsodizes about a new miracle cure for his imaginary illness, or when Ben's advances intensify—animated numbers flow from her hands like an educational superhero. An introductory cartoon bedtime story returns as a nightmare of dismemberment. After a teary epiphany clearly legible on Alba's pouty face, her voice-over confirms: "He didn't get it, but I finally did." The audience gets it after the first half-hour: the only thing greater than Mona's childhood bliss will be a happy family of her own, and that's where all the highly visible signs point.