Moose has his hands full during the summer of 1936 watching his autistic sister, Natalie, and the warden's daughter, Piper, and trying to get on a baseball team by proving he knows Al Capone.
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.