Grandpa Gus gets in a pout because everyone tells him to get out of their way one day, so he leaves a note and runs away and decides to live on top of a nearby mountain by himself.
Since the next day is his birthday, the Pipkin family all feels rather badly, and set off with a cake to find grandpa, who . And grandpa feels useful again.
I don't like stories about guilt-tripping, immature adults. That's no way for anyone to behave, least of all someone who should, in theory, have a lifetime of wisdom under their belts.
I was very taken with the illustrations. Unfortunately, Grandpa Gus will need to reconcile himself to the obliviousness and sporadic attentions of his family if he wants to live in comfort rather than in a shack on the mountain.