After witnessing her mother's death 3 years ago, 12-year-old Sam Pepper has never been able to move on. With her reclusive nature and place at the 'nerd table', Sam is an easy target for bullying, even from her former friend PJ. One day, when PJ humiliates her in front of all their classmates, Sam decides she's finally had enough. Her imagination is sparked by an ad in a comic book, offering to deliver all the parts you need to build your own 'Monster'. Finally, Sam is able to give PJ a taste of her own medicine. But just as her life takes a turn for the better, Sam's father reveals he's proposed to his girlfriend. Suddenly, her life's changing in more ways than she expected, and unable to face the state of her family, Sam relies on her monster to stop her from getting a new mum.