Onion O'Brien is in trouble, again. This time he and the rest of the Five O's are trying to stop the destruction of the Valley, the local wasteland where they hang out. But Mayor Ronald Bump has other ideas - he wants to build new apartments there, so he sets local guards The Ferg and Judge on the children.
As if things aren't bad enough, there's a new teacher in their school acting very suspiciously. The Five O's can find out his secret...