Melody is a 12-year-old girl living with cerebral palsy. Because she cannot walk or talk, she relies on a wheelchair and an assistive communication device called Elvira. She possesses a brilliant mind and a deep curiosity about the world around her. An unexpected medical emergency pushes her into the public eye and leads to a special trip to London.

Miss Gertie is the Brooks family's elderly neighbor who lives quietly by herself in Ohio. She is a former British actress who withdrew from public life following the death of her husband. Her trip back to London gives her a chance to reconnect with her roots and her love for the theater.

Sky is Miss Gertie's 14-year-old great-niece. Because her parents work in the foreign service, she moves constantly and struggles to maintain long-term friendships. She quickly bonds with Melody over their shared love of music and fashion.

Mrs. V is an older neighbor who frequently acts as an aide for Melody. She is instrumental in acquiring Elvira and consistently encourages Melody to stretch her boundaries. She travels to London to provide full-time assistance during the conference.

Oliver is Sky's older brother. He spends his summer interning at the Globe theater in London. Friendly and welcoming, he secures theater tickets for his sister and her friends and guides them through the city.

Teddy is a cheerful cab driver who ferries Melody and her companions around London. He happens to be an old university classmate of Miss Gertie and holds fond memories of her acting career.

Bethany is a colorful-haired delegate at the symposium. A former dancer who sustained a spinal cord injury, she now participates in wheelchair ballet and works on accessibility in dance.

Penny is Melody's five-year-old sister. She is highly energetic and loves everything related to makeup. Her youthful enthusiasm brings constant motion to the family home.

Melody's mother works as a nurse. She handles the complex logistics of her daughter's daily needs and ensures Melody is dressed up and prepared for her television appearances.

Melody's father is a supportive presence who helps his family prepare for their media interviews. He manages his own anxiety about the logistics of international travel while encouraging his daughters.

Noah is a boy Melody met at a summer camp for children with disabilities. He stays in touch with her and invites her to an amusement park.

Jeffrey is the emergency operator who answers Melody's 911 call. He correctly identifies that she is using a communication board and patiently gathers the necessary information to dispatch an ambulance.

Mr. Hammond is the director working at the Globe theater. When one of his actresses is delayed, he remembers Miss Gertie's talent and begs her to step into the role.

Ian is a singer in Melody's favorite boy band, Double Trouble. Upon hearing that accessibility issues barred Melody from his concert, he arranges an exclusive recording session for her group.

Charlene acts as the emcee for the international symposium. She encourages the young innovators to share their world-changing ideas.

Audrey runs the brainstorming session at the conference. She reassures the children that they do not have to present their ideas if they feel uncomfortable.

The crown prince of England attends the I.D.E.A. conference. He enthusiastically supports the young delegates as they present their inventions.