Matilda "Tillie" Hunsdorfer is the main character of Paul Zindel's play The Effect of Gamma Rays on Man-in-the-Moon Marigolds. Everything that is known about Tillie throughout the play comes from three sources: from Tillie's monologues, from her mother Beatrice's words, and from the words of Tillie's sister, Ruth.
From the information that is given, Tillie's past can be easily described, in not so many words, as chaotic. The youngest in the family, Tillie was born to a dysfunctional marriage made up of her mother, an unstable, and narcissistic alcoholic, and her father who presumably "deserved" the stroke that killed him, according to Beatrice. From a very young age, Tillie has been somewhat warding off the toxic "radiation" which has become the constant exposure to her mother's bipolar fits. As a result, Tillie has developed into a very shy, but still extremely inquisitive and bright student.
Tillie's present is just as chaotic as her past. However, her character shows a resilience that can only be explained by assuming that it is her ultimate defense mechanism. As the youngest child of a family of three, she is also the least dysfunctional. Picked on by her mother, Tillie is often left home from school to do household chores, thus encouraging a form of truancy from which Tillie, thankfully, comes out unscathed. If anything, she fervently uses her inquisitive nature to make the most out of her school days, and she actively engages in a science project involving marigolds exposed to radiation.
Hence, her science project becomes a form of psychological or cathartic task that could be described as a form of epiphany: she has to correlate the effects of the exposure to toxic rays on delicate flowers; this shows affinity to the current conditions taking place at the Hunsdorfer home, where Beatrice's toxic nature is greatly affecting her two young daughters.
Yet, Tillie's present is, perhaps, her lifesaver. As she prepares for this project she has had to battle her mother's insults, her sister's scornful remarks, her physical absences from school, and the overall atmosphere of discord that permeates the home. However, all of these obstacles are nothing to Tillie but merely that: bumps on the road to something greater.
Although nothing in the play implies that Tillie's future will be brighter, there is still a glimmer of hope in the fact that nothing shows that Tillie will change. The success of her science project might actually render her a stronger and more psychologically independent girl. This is because she found a niche in science. She has found the one goal that helps her look up at the stars, even if she is looking up from the depths of misery. It is safe to assume that Tillie will use science, much like Paul Zindel did himself, as a way to overcome the life obstacles brought in by a family from which she has to protect herself.