The Flanagan family lived in Santa Monica, California. They then move to Alcatraz Island when their dad is given a job guarding towers there, so his sister, Natalie, can go to a special school just for autistic children. Moose is forced to leave all of his friends behind him and pick up somewhere in a totally different place and lifestyle. Staying out of trouble is especially difficult for Moose when the warden’s daughter, Piper, is around. She is a pretty girl and a manipulative troublemaker. From selling their laundry services, to writing secret letters to the famous Al Capone, Piper is always finding different ways to get Moose into trouble.
Natalie lasts a day and a half at the Esther P. Marinoff School, so his parents ask him to watch her while they are at work. He is a responsible brother, but the burdens placed on him are sometimes too much to bear, and just trying to keep out of trouble with Piper around is a full-time job. When he finds out Natalie was rejected from the school, he writes a secret note to Al Capone, asking him to help her. He does, and Natalie is accepted into a school for older autistic children.