Mike, a 58-year-old biker with tattoos and a rough exterior, volunteers at a children's hospital, reading to sick kids. One day, he meets Amara, a 7-year-old girl with stage four neuroblastoma, who’s been abandoned by her mother and has no family. Despite her grim prognosis, Amara asks Mike if he would be her daddy until she dies.

Mike is heartbroken by her request but agrees, telling her he might not be good at being a dad. Amara lights up and responds, "That's okay. You can practice on me." Mike and his motorcycle club make her hospital room feel like home, and he visits every day, reading stories and singing songs, forming an unbreakable bond.

The doctors are baffled as Amara’s condition slowly improves. On her eighth birthday, she walks for the first time in months, and two weeks later, her tumors begin shrinking. After 18 months, Amara leaves the hospital cancer-free, and the club throws her a huge celebration. She’s now 15, still calls Mike "Daddy," and every Thursday, they ride back to the hospital together to bring comfort to other sick kids.