Six-year-old Lilo Pelekai is taken care of by her older sister Nani. Nani has to work a lot, so the girl is often left alone. One day, a neighbor suggests taking a dog from the shelter to help the girl cope with her loneliness. However, from the shelter, Lilo takes a cute alien instead of a dog. The girl gives her new pet the nickname Stitch, but on his home planet he is nicknamed Experiment 626. He is a fugitive from the galactic police and a product of genetic experiments, characterized by a penchant for destruction, the ability to learn quickly and almost total invulnerability.