In the early 1960s, P.L. Travers, a curt and uncompromising British author, finds herself in financial straits despite the success of her children’s books featuring the beloved nanny Mary Poppins. The Walt Disney Company has been seeking the film rights for twenty years, keen to adapt the series for the big screen. Walt Disney himself, driven by a promise to his daughters, personally invites Travers to Los Angeles to discuss the adaptation. Initially reluctant and protective of her work, Travers eventually agrees, but her stiff and irascible demeanor spurs tension from the moment she steps foot in California.

Once in Los Angeles, Travers meets with the creative team assigned to bring Mary Poppins to life, including scriptwriter Don DaGradi and the songwriting Sherman Brothers. Despite Disney’s charm offensive and enthusiasm for the project, Travers is highly critical and disapproving of the proposed treatment for her character, particularly the animated sequences and musical numbers, which she finds frivolous. Alongside her negotiations and clashes with the Disney team, the story delves into her difficult childhood in Australia, exploring the complex relationship she had with her loving but troubled father. These flashbacks provide insight into the origins of her character Mary Poppins and the deeper meanings Travers has infused into her work, revealing her emotional attachment and reasons for her reluctance to hand over the rights.