In a nutshell:
The Wupis have a mission: they have to spy out Earth! To do this they obviously have to go on a trip to town instead of only hiding in the attic of Ben's home. But while on their expedition, Wupi girl Triximixi is suddenly abducted by two nasty secret service agents. For Ben, the cross-eyed opossum Otto and Wupi boy Cameo it is a clear-cut case: they will have to rescue their friend from the super-secret secret service headquarters!