[2] The novel centers on 18-year-old Madeline Whittier, who is being treated for severe combined immunodeficiency (SCID), also known as "bubble baby disease".

[3] The story follows 18-year-old Madeline Whittier, also known as Maddy, a half-Japanese, half-African-American who is being treated for severe combined immunodeficiency (SCID), and therefore is not allowed to leave her house or interact with anything that has not been "sanitized".

Her world consists of her doctor mother Pauline, her nurse Carla, and the books she finds comfort in; her father and brother died a long time ago in a car accident.

A month later, Maddy sees Olly, Kara, and their mother loading their belongings into a moving van while their father is at work, escaping his tyranny.

Maddy, angry and panicked, searches her mother's medical files but doesn’t find the test results or doctor's notes that would confirm she had SCID.

Pauline says that right after the car accident, Maddy got very sick and, not wanting to lose her, decided to think she had SCID and needed to be kept away from the world.

A reviewer for The Guardian wrote about the book: "The way the author describes Madeline's world using such beautiful imagery makes the reader appreciate the little things in life".