Zed (Jack Black) is a hunter and Oh (Michael Cera) is a gatherer. After being informed that Zed ate from the Tree of Knowledge of Good and Evil, the shaman (Bill Hader) and Marlak (Matthew Willig) banish him from the tribe. After Zed burns down the village by accident Oh decides to go with Zed on his journey to discover all the world has to offer. Along the way, they encounter Cain and Abel (David Cross and Paul Rudd). Cain kills Abel and informs Zed and Oh that they must escape with him or else be accused of killing Abel.