Just as thirteen year-old Edith Walker is about to leave childhood behind, she thinks she spots a unicorn high on a slope while hiking. Her daydreamer father Henry convinces her that what she's seen is real. Edith's sighting of the fabled creature -- and her unfailing belief that the imaginary creature will eventually be found -- sets in motion a series of events that impact the next decade of her life. Edith grows up in her big sister Vivienne's shadow. While the beautiful Viv is forced by the girls' overbearing mother Constance to compete in child beauty pageants, plain-looking Edith follows in her father's footsteps, collecting oddities, studying coins and reading from moldy books that only serve to exacerbate her asthma. Eventually, a family trip to the Rocky Mountains and a chance encounter with a handsome geology student named Liam changes the course of the sisters' relationship forever. As Viv rebels against her mother and pageantry to become a painter, she embarks on a downward spiral into addiction. Edith then finds herself torn between a desire to save her sister and pursuing her own love for Liam.