One bright morning Big decides that he will explore the road outside the house, because you can find all sorts of excitement when ambling slowly down a road. He sings a song about the joys of such a walk. Small is excited at going on a trip and packs a bag, but after taking a couple of steps Small has to go back to get some things that he had forgotten: the camera, the clock, a banana...
When he gets back he finds that Big is sitting on the grass and singing a song about sitting on the grass. After a couple more steps Small realises he should have brought the wagon to put all their stuff in. When he returns with the wagon Big is sitting on the grass and singing another song...
The journey progresses very slowly and soon it's almost dark. They look back to see the house and decide that it looks very welcoming. They turn around and go back home: walking down the road can wait until another day.