When Moose Flanagan and his family move home, yet again, and become residents of the famous prison island Alcatraz, things get interesting. First of all, they share the island with a few other families and a lot of pretty heavy-duty criminals including Al Capone. And secondly, Moose's sister is starting a new school, which everyone hopes will help her become more integrated with those around her.

When Moose comes up with some pretty cunning money-making schemes based on his famous co-residents, he does not count on his sister becoming inadvertently involved.