I am Sam (plot commentary)

Sam (played by Sean Penn) who works at Starbucks is an adult, but his intelligence level is only 7 years old. By chance, he took in a homeless girl. The woman helped Sam give birth to a daughter and then disappeared without a trace. He named his daughter Lucy (Dakota Fanning) because he liked the Beatles' "Lucy in the Sky with Diamonds" the most. He loved his children very much. As Lucy grew up slowly under Sam's careful care, she found that her father could not understand slightly more complicated stories. She is refusing to grow up and wants to be like her father. The life of father and daughter is so happy. District education officials discovered this special family. They believed that Sam was unable to take care of Lucy, so they took Lucy away. The heartbroken Sam wanted to earn Lucy's custody rights, so he self-righteously went to find the best lawyer in the area...