 Why does Purnie save the humans?
With everything around him in a state of perfect tableau, Purnie hurried toward the ocean. He ran along feeling sorry for four-year-olds, and even for those who were only four and a half, for they were babies and wouldn't dare try slipping away to the ocean alone. When Purnie had stopped time, the bees—like all the other creatures he met—had been arrested in their native activities, and he knew that as soon as he resumed time, everything would pick up where it had left off. He chose to ignore the negative maxim that "small children who stop time without an adult being present, may not live to regret it." Overhead, a flock of spora were frozen in a steep glide, preparatory to a beach landing. Further down the beach was a pair of two-legged animals poised in mid-step, facing the spot where Purnie now stood. It was time itself that Purnie had stopped, not the world around him. He scampered around the rockpile and down the sandy cliff to meet the tripons who, to him, had just come to life. The tripon thought Purnie's feat was superb. Purnie ran from pillar to post, trying to see and do everything at once. Purnie's invitation got nothing more than startled glance from the animals who quickly returned to their chatter. As Purnie followed along, a leg shot out at him and missed. Purnie shrieked with joy at this new frolic and promptly stood on his head.
 Purnie blames himself for the avalanche that trapped his friends.
 Purnie is worried other humans will come to his planet if he doesn't save this group.  Purnie blames himself for the avalanche that trapped his friends.  Purnie thinks the humans are his friends.  Purnie thinks the humans can cure his radiation poisoning.