Unable to face the fact that her husband committed suicide, Gilbert's (Johnny Depp) mother kept eating, causing her weight to surge to 600 pounds and making it difficult to move. Gilbert's mentally retarded brother Arnie (Leonardo Dicaprio) was diagnosed by the doctor at birth that he would not live more than ten years old, but he is about to celebrate his 18th birthday, and his youngest sister Ellen is in rebellious adolescence. The livelihood of the entire family and Arnie's daily life have become Gilbert's entire life, and his sister is his only helper. Betsy (Juliette Lewis), who travels around and is lively and cheerful, passed by the town and fell in love with Gilbert at first sight. The two soon immersed themselves in sweet love. Betsy's passion for life also made Gilbert gradually realize that in addition to his family, he should also have his own pursuits in life. Arnie is about to turn 18, which is his mother's last wish. When all this is over, Gilbert can have a different sky.