Facing another long winter hibernating in their dam, Norb and Dag decide to "Go South". It's all sun and fun, but eventually the boys find out there are good reasons why beavers don't migrate for winter.

The beavers are launched into space to see if they can build a dam in zero gravity. Once their scientific usefulness is over, they find themselves abandoned in space. The beavers must put aside their differences and band together to avert their almost certain doom

Norb befriends Stump (an actual tree stump that the boys chewed down). Despite Dag's jealousy, Norb realizes he hasn't lost a brother but gained a friend.