A twelve-year-old boy named Moose moves to Alcatraz Island in 1935 when guards' families were housed there, and has to contend with his extraordinary new environment in addition to life with his autistic sister.

Moose Flanagan, who lives on Alcatraz along with his family and the families of the other prison guards, is frightened when he discovers that noted gangster Al Capone, a prisoner there, wants a favor in return for the help that he secretly gave Moose.

Moose Flanagan, who lives on Alcatraz along with his family and the families of the other prison guards, faces new challenges when his father is promoted to Associate Warden.