I'm getting pretty close to the part of the game where you have to go to the Prison Island. I've played a lot of games where the last level is the last level, and you can't leave it to return anywhere. Is Dead Island like that, in that you can't leave the Prison Island once you go there?
Sorry, no you can't. Once inside the prison you are set to finish the game. They even warn you when you are about to leave the lab and go that you can't go back after this point. However, you can restart the story when you finish the game. You keep all weapons( unless starting a new character for the achievement) and you keep your level and money.
Taken from here.